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HTML

              
                <script src="https://maps.googleapis.com/maps/api/js?&sensor=false&v=3"></script>

<div id="map"></div>

<a href="https://ianchuu.com/2017/12/11/Google%20Map%20marker%20cluster%20%E6%A8%99%E8%A8%98%E4%BD%BF%E7%94%A8%E6%95%99%E5%AD%B8/" target"_blank">more guide info</a>
              
            
!

CSS

              
                #map {
  width:100%;
  height:250px;
}
   .labels {
     color: red;
     background-color: white;
     font-family: "Lucida Grande", "Arial", sans-serif;
     font-size: 10px;
     font-weight: bold;
     text-align: center;
     width: 80px;     
     border: 2px solid black;
     white-space: nowrap;
   }
              
            
!

JS

              
                // ==ClosureCompiler==
// @compilation_level ADVANCED_OPTIMIZATIONS
// @externs_url http://closure-compiler.googlecode.com/svn/trunk/contrib/externs/maps/google_maps_api_v3_3.js
// ==/ClosureCompiler==

/**
 * @name MarkerClusterer for Google Maps v3
 * @version version 1.0.1
 * @author Luke Mahe
 * @fileoverview
 * The library creates and manages per-zoom-level clusters for large amounts of
 * markers.
 * <br/>
 * This is a v3 implementation of the
 * <a href="http://gmaps-utility-library-dev.googlecode.com/svn/tags/markerclusterer/"
 * >v2 MarkerClusterer</a>.
 */

/**
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


/**
 * A Marker Clusterer that clusters markers.
 *
 * @param {google.maps.Map} map The Google map to attach to.
 * @param {Array.<google.maps.Marker>=} opt_markers Optional markers to add to
 *   the cluster.
 * @param {Object=} opt_options support the following options:
 *     'gridSize': (number) The grid size of a cluster in pixels.
 *     'maxZoom': (number) The maximum zoom level that a marker can be part of a
 *                cluster.
 *     'zoomOnClick': (boolean) Whether the default behaviour of clicking on a
 *                    cluster is to zoom into it.
 *     'imagePath': (string) The base URL where the images representing
 *                  clusters will be found. The full URL will be:
 *                  {imagePath}[1-5].{imageExtension}
 *                  Default: '../images/m'.
 *     'imageExtension': (string) The suffix for images URL representing
 *                       clusters will be found. See _imagePath_ for details.
 *                       Default: 'png'.
 *     'averageCenter': (boolean) Whether the center of each cluster should be
 *                      the average of all markers in the cluster.
 *     'minimumClusterSize': (number) The minimum number of markers to be in a
 *                           cluster before the markers are hidden and a count
 *                           is shown.
 *     'styles': (object) An object that has style properties:
 *       'url': (string) The image url.
 *       'height': (number) The image height.
 *       'width': (number) The image width.
 *       'anchor': (Array) The anchor position of the label text.
 *       'textColor': (string) The text color.
 *       'textSize': (number) The text size.
 *       'backgroundPosition': (string) The position of the backgound x, y.
 * @constructor
 * @extends google.maps.OverlayView
 */
function MarkerClusterer(map, opt_markers, opt_options) {
    // MarkerClusterer implements google.maps.OverlayView interface. We use the
    // extend function to extend MarkerClusterer with google.maps.OverlayView
    // because it might not always be available when the code is defined so we
    // look for it at the last possible moment. If it doesn't exist now then
    // there is no point going ahead :)
    this.extend(MarkerClusterer, google.maps.OverlayView);
    this.map_ = map;

    /**
     * @type {Array.<google.maps.Marker>}
     * @private
     */
    this.markers_ = [];

    /**
     *  @type {Array.<Cluster>}
     */
    this.clusters_ = [];

    this.sizes = [53, 56, 66, 78, 90];

    /**
     * @private
     */
    this.styles_ = [];

    /**
     * @type {boolean}
     * @private
     */
    this.ready_ = false;

    var options = opt_options || {};

    /**
     * @type {number}
     * @private
     */
    this.gridSize_ = options['gridSize'] || 60;

    /**
     * @private
     */
    this.minClusterSize_ = options['minimumClusterSize'] || 2;


    /**
     * @type {?number}
     * @private
     */
    this.maxZoom_ = options['maxZoom'] || null;

    this.styles_ = options['styles'] || [];

    /**
     * @type {string}
     * @private
     */
    this.imagePath_ = options['imagePath'] ||
        this.MARKER_CLUSTER_IMAGE_PATH_;

    /**
     * @type {string}
     * @private
     */
    this.imageExtension_ = options['imageExtension'] ||
        this.MARKER_CLUSTER_IMAGE_EXTENSION_;

    /**
     * @type {boolean}
     * @private
     */
    this.zoomOnClick_ = true;

    if (options['zoomOnClick'] != undefined) {
        this.zoomOnClick_ = options['zoomOnClick'];
    }

    /**
     * @type {boolean}
     * @private
     */
    this.averageCenter_ = false;

    if (options['averageCenter'] != undefined) {
        this.averageCenter_ = options['averageCenter'];
    }

    this.setupStyles_();

    this.setMap(map);

    /**
     * @type {number}
     * @private
     */
    this.prevZoom_ = this.map_.getZoom();

    // Add the map event listeners
    var that = this;
    google.maps.event.addListener(this.map_, 'zoom_changed', function() {
        // Determines map type and prevent illegal zoom levels
        var zoom = that.map_.getZoom();
        var minZoom = that.map_.minZoom || 0;
        var maxZoom = Math.min(that.map_.maxZoom || 100,
            that.map_.mapTypes[that.map_.getMapTypeId()].maxZoom);
        zoom = Math.min(Math.max(zoom, minZoom), maxZoom);

        if (that.prevZoom_ != zoom) {
            that.prevZoom_ = zoom;
            that.resetViewport();
        }
    });

    google.maps.event.addListener(this.map_, 'idle', function() {
        that.redraw();
    });

    // Finally, add the markers
    if (opt_markers && (opt_markers.length || Object.keys(opt_markers).length)) {
        this.addMarkers(opt_markers, false);
    }
}


/**
 * The marker cluster image path.
 *
 * @type {string}
 * @private
 */
MarkerClusterer.prototype.MARKER_CLUSTER_IMAGE_PATH_ = '../images/m';


/**
 * The marker cluster image path.
 *
 * @type {string}
 * @private
 */
MarkerClusterer.prototype.MARKER_CLUSTER_IMAGE_EXTENSION_ = 'png';


/**
 * Extends a objects prototype by anothers.
 *
 * @param {Object} obj1 The object to be extended.
 * @param {Object} obj2 The object to extend with.
 * @return {Object} The new extended object.
 * @ignore
 */
MarkerClusterer.prototype.extend = function(obj1, obj2) {
    return (function(object) {
        for (var property in object.prototype) {
            this.prototype[property] = object.prototype[property];
        }
        return this;
    }).apply(obj1, [obj2]);
};


/**
 * Implementaion of the interface method.
 * @ignore
 */
MarkerClusterer.prototype.onAdd = function() {
    this.setReady_(true);
};

/**
 * Implementaion of the interface method.
 * @ignore
 */
MarkerClusterer.prototype.draw = function() {};

/**
 * Sets up the styles object.
 *
 * @private
 */
MarkerClusterer.prototype.setupStyles_ = function() {
    if (this.styles_.length) {
        return;
    }

    for (var i = 0, size; size = this.sizes[i]; i++) {
        this.styles_.push({
            url: this.imagePath_ + (i + 1) + '.' + this.imageExtension_,
            height: size,
            width: size
        });
    }
};

/**
 *  Fit the map to the bounds of the markers in the clusterer.
 */
MarkerClusterer.prototype.fitMapToMarkers = function() {
    var markers = this.getMarkers();
    var bounds = new google.maps.LatLngBounds();
    for (var i = 0, marker; marker = markers[i]; i++) {
        bounds.extend(marker.getPosition());
    }

    this.map_.fitBounds(bounds);
};


/**
 *  Sets the styles.
 *
 *  @param {Object} styles The style to set.
 */
MarkerClusterer.prototype.setStyles = function(styles) {
    this.styles_ = styles;
};


/**
 *  Gets the styles.
 *
 *  @return {Object} The styles object.
 */
MarkerClusterer.prototype.getStyles = function() {
    return this.styles_;
};


/**
 * Whether zoom on click is set.
 *
 * @return {boolean} True if zoomOnClick_ is set.
 */
MarkerClusterer.prototype.isZoomOnClick = function() {
    return this.zoomOnClick_;
};

/**
 * Whether average center is set.
 *
 * @return {boolean} True if averageCenter_ is set.
 */
MarkerClusterer.prototype.isAverageCenter = function() {
    return this.averageCenter_;
};


/**
 *  Returns the array of markers in the clusterer.
 *
 *  @return {Array.<google.maps.Marker>} The markers.
 */
MarkerClusterer.prototype.getMarkers = function() {
    return this.markers_;
};


/**
 *  Returns the number of markers in the clusterer
 *
 *  @return {Number} The number of markers.
 */
MarkerClusterer.prototype.getTotalMarkers = function() {
    return this.markers_.length;
};


/**
 *  Sets the max zoom for the clusterer.
 *
 *  @param {number} maxZoom The max zoom level.
 */
MarkerClusterer.prototype.setMaxZoom = function(maxZoom) {
    this.maxZoom_ = maxZoom;
};


/**
 *  Gets the max zoom for the clusterer.
 *
 *  @return {number} The max zoom level.
 */
MarkerClusterer.prototype.getMaxZoom = function() {
    return this.maxZoom_;
};


/**
 *  The function for calculating the cluster icon image.
 *
 *  @param {Array.<google.maps.Marker>} markers The markers in the clusterer.
 *  @param {number} numStyles The number of styles available.
 *  @return {Object} A object properties: 'text' (string) and 'index' (number).
 *  @private
 */
MarkerClusterer.prototype.calculator_ = function(markers, numStyles) {
    var index = 0;
    var count = markers.length;
    var dv = count;
    while (dv !== 0) {
        dv = parseInt(dv / 10, 10);
        index++;
    }
    var price = 0;
    for (var i = 0; i < markers.length; i++) {
        price += Number(markers[i].dataPrice);
    }
    price = Math.floor(price/count);
    
    index = Math.min(index, numStyles);
    return {
        text: count + ' 筆<br/>A. NT' + price,
        index: index
    };
};


/**
 * Set the calculator function.
 *
 * @param {function(Array, number)} calculator The function to set as the
 *     calculator. The function should return a object properties:
 *     'text' (string) and 'index' (number).
 *
 */
MarkerClusterer.prototype.setCalculator = function(calculator) {
    this.calculator_ = calculator;
};


/**
 * Get the calculator function.
 *
 * @return {function(Array, number)} the calculator function.
 */
MarkerClusterer.prototype.getCalculator = function() {
    return this.calculator_;
};


/**
 * Add an array of markers to the clusterer.
 *
 * @param {Array.<google.maps.Marker>} markers The markers to add.
 * @param {boolean=} opt_nodraw Whether to redraw the clusters.
 */
MarkerClusterer.prototype.addMarkers = function(markers, opt_nodraw) {
    if (markers.length) {
        for (var i = 0, marker; marker = markers[i]; i++) {
            this.pushMarkerTo_(marker);
        }
    } else if (Object.keys(markers).length) {
        for (var marker in markers) {
            this.pushMarkerTo_(markers[marker]);
        }
    }
    if (!opt_nodraw) {
        this.redraw();
    }
};


/**
 * Pushes a marker to the clusterer.
 *
 * @param {google.maps.Marker} marker The marker to add.
 * @private
 */
MarkerClusterer.prototype.pushMarkerTo_ = function(marker) {
    marker.isAdded = false;
    if (marker['draggable']) {
        // If the marker is draggable add a listener so we update the clusters on
        // the drag end.
        var that = this;
        google.maps.event.addListener(marker, 'dragend', function() {
            marker.isAdded = false;
            that.repaint();
        });
    }
    this.markers_.push(marker);
};


/**
 * Adds a marker to the clusterer and redraws if needed.
 *
 * @param {google.maps.Marker} marker The marker to add.
 * @param {boolean=} opt_nodraw Whether to redraw the clusters.
 */
MarkerClusterer.prototype.addMarker = function(marker, opt_nodraw) {
    this.pushMarkerTo_(marker);
    if (!opt_nodraw) {
        this.redraw();
    }
};


/**
 * Removes a marker and returns true if removed, false if not
 *
 * @param {google.maps.Marker} marker The marker to remove
 * @return {boolean} Whether the marker was removed or not
 * @private
 */
MarkerClusterer.prototype.removeMarker_ = function(marker) {
    var index = -1;
    if (this.markers_.indexOf) {
        index = this.markers_.indexOf(marker);
    } else {
        for (var i = 0, m; m = this.markers_[i]; i++) {
            if (m == marker) {
                index = i;
                break;
            }
        }
    }

    if (index == -1) {
        // Marker is not in our list of markers.
        return false;
    }

    marker.setMap(null);

    this.markers_.splice(index, 1);

    return true;
};


/**
 * Remove a marker from the cluster.
 *
 * @param {google.maps.Marker} marker The marker to remove.
 * @param {boolean=} opt_nodraw Optional boolean to force no redraw.
 * @return {boolean} True if the marker was removed.
 */
MarkerClusterer.prototype.removeMarker = function(marker, opt_nodraw) {
    var removed = this.removeMarker_(marker);

    if (!opt_nodraw && removed) {
        this.resetViewport();
        this.redraw();
        return true;
    } else {
        return false;
    }
};


/**
 * Removes an array of markers from the cluster.
 *
 * @param {Array.<google.maps.Marker>} markers The markers to remove.
 * @param {boolean=} opt_nodraw Optional boolean to force no redraw.
 */
MarkerClusterer.prototype.removeMarkers = function(markers, opt_nodraw) {
    // create a local copy of markers if required
    // (removeMarker_ modifies the getMarkers() array in place)
    var markersCopy = markers === this.getMarkers() ? markers.slice() : markers;
    var removed = false;

    for (var i = 0, marker; marker = markersCopy[i]; i++) {
        var r = this.removeMarker_(marker);
        removed = removed || r;
    }

    if (!opt_nodraw && removed) {
        this.resetViewport();
        this.redraw();
        return true;
    }
};


/**
 * Sets the clusterer's ready state.
 *
 * @param {boolean} ready The state.
 * @private
 */
MarkerClusterer.prototype.setReady_ = function(ready) {
    if (!this.ready_) {
        this.ready_ = ready;
        this.createClusters_();
    }
};


/**
 * Returns the number of clusters in the clusterer.
 *
 * @return {number} The number of clusters.
 */
MarkerClusterer.prototype.getTotalClusters = function() {
    return this.clusters_.length;
};


/**
 * Returns the google map that the clusterer is associated with.
 *
 * @return {google.maps.Map} The map.
 */
MarkerClusterer.prototype.getMap = function() {
    return this.map_;
};


/**
 * Sets the google map that the clusterer is associated with.
 *
 * @param {google.maps.Map} map The map.
 */
MarkerClusterer.prototype.setMap = function(map) {
    this.map_ = map;
};


/**
 * Returns the size of the grid.
 *
 * @return {number} The grid size.
 */
MarkerClusterer.prototype.getGridSize = function() {
    return this.gridSize_;
};


/**
 * Sets the size of the grid.
 *
 * @param {number} size The grid size.
 */
MarkerClusterer.prototype.setGridSize = function(size) {
    this.gridSize_ = size;
};


/**
 * Returns the min cluster size.
 *
 * @return {number} The grid size.
 */
MarkerClusterer.prototype.getMinClusterSize = function() {
    return this.minClusterSize_;
};

/**
 * Sets the min cluster size.
 *
 * @param {number} size The grid size.
 */
MarkerClusterer.prototype.setMinClusterSize = function(size) {
    this.minClusterSize_ = size;
};


/**
 * Extends a bounds object by the grid size.
 *
 * @param {google.maps.LatLngBounds} bounds The bounds to extend.
 * @return {google.maps.LatLngBounds} The extended bounds.
 */
MarkerClusterer.prototype.getExtendedBounds = function(bounds) {
    var projection = this.getProjection();

    // Turn the bounds into latlng.
    var tr = new google.maps.LatLng(bounds.getNorthEast().lat(),
        bounds.getNorthEast().lng());
    var bl = new google.maps.LatLng(bounds.getSouthWest().lat(),
        bounds.getSouthWest().lng());

    // Convert the points to pixels and the extend out by the grid size.
    var trPix = projection.fromLatLngToDivPixel(tr);
    trPix.x += this.gridSize_;
    trPix.y -= this.gridSize_;

    var blPix = projection.fromLatLngToDivPixel(bl);
    blPix.x -= this.gridSize_;
    blPix.y += this.gridSize_;

    // Convert the pixel points back to LatLng
    var ne = projection.fromDivPixelToLatLng(trPix);
    var sw = projection.fromDivPixelToLatLng(blPix);

    // Extend the bounds to contain the new bounds.
    bounds.extend(ne);
    bounds.extend(sw);

    return bounds;
};


/**
 * Determins if a marker is contained in a bounds.
 *
 * @param {google.maps.Marker} marker The marker to check.
 * @param {google.maps.LatLngBounds} bounds The bounds to check against.
 * @return {boolean} True if the marker is in the bounds.
 * @private
 */
MarkerClusterer.prototype.isMarkerInBounds_ = function(marker, bounds) {
    return bounds.contains(marker.getPosition());
};


/**
 * Clears all clusters and markers from the clusterer.
 */
MarkerClusterer.prototype.clearMarkers = function() {
    this.resetViewport(true);

    // Set the markers a empty array.
    this.markers_ = [];
};


/**
 * Clears all existing clusters and recreates them.
 * @param {boolean} opt_hide To also hide the marker.
 */
MarkerClusterer.prototype.resetViewport = function(opt_hide) {
    // Remove all the clusters
    for (var i = 0, cluster; cluster = this.clusters_[i]; i++) {
        cluster.remove();
    }

    // Reset the markers to not be added and to be invisible.
    for (var i = 0, marker; marker = this.markers_[i]; i++) {
        marker.isAdded = false;
        if (opt_hide) {
            marker.setMap(null);
        }
    }

    this.clusters_ = [];
};

/**
 *
 */
MarkerClusterer.prototype.repaint = function() {
    var oldClusters = this.clusters_.slice();
    this.clusters_.length = 0;
    this.resetViewport();
    this.redraw();

    // Remove the old clusters.
    // Do it in a timeout so the other clusters have been drawn first.
    window.setTimeout(function() {
        for (var i = 0, cluster; cluster = oldClusters[i]; i++) {
            cluster.remove();
        }
    }, 0);
};


/**
 * Redraws the clusters.
 */
MarkerClusterer.prototype.redraw = function() {
    this.createClusters_();
};


/**
 * Calculates the distance between two latlng locations in km.
 * @see http://www.movable-type.co.uk/scripts/latlong.html
 *
 * @param {google.maps.LatLng} p1 The first lat lng point.
 * @param {google.maps.LatLng} p2 The second lat lng point.
 * @return {number} The distance between the two points in km.
 * @private
 */
MarkerClusterer.prototype.distanceBetweenPoints_ = function(p1, p2) {
    if (!p1 || !p2) {
        return 0;
    }

    var R = 6371; // Radius of the Earth in km
    var dLat = (p2.lat() - p1.lat()) * Math.PI / 180;
    var dLon = (p2.lng() - p1.lng()) * Math.PI / 180;
    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(p1.lat() * Math.PI / 180) * Math.cos(p2.lat() * Math.PI / 180) *
        Math.sin(dLon / 2) * Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    var d = R * c;
    return d;
};


/**
 * Add a marker to a cluster, or creates a new cluster.
 *
 * @param {google.maps.Marker} marker The marker to add.
 * @private
 */
MarkerClusterer.prototype.addToClosestCluster_ = function(marker) {
    var distance = 40000; // Some large number
    var clusterToAddTo = null;
    var pos = marker.getPosition();
    for (var i = 0, cluster; cluster = this.clusters_[i]; i++) {
        var center = cluster.getCenter();
        if (center) {
            var d = this.distanceBetweenPoints_(center, marker.getPosition());
            if (d < distance) {
                distance = d;
                clusterToAddTo = cluster;
            }
        }
    }

    if (clusterToAddTo && clusterToAddTo.isMarkerInClusterBounds(marker)) {
        clusterToAddTo.addMarker(marker);
    } else {
        var cluster = new Cluster(this);
        cluster.addMarker(marker);
        this.clusters_.push(cluster);
    }
};


/**
 * Creates the clusters.
 *
 * @private
 */
MarkerClusterer.prototype.createClusters_ = function() {
    if (!this.ready_) {
        return;
    }

    // Get our current map view bounds.
    // Create a new bounds object so we don't affect the map.
    var mapBounds = new google.maps.LatLngBounds(this.map_.getBounds().getSouthWest(),
        this.map_.getBounds().getNorthEast());
    var bounds = this.getExtendedBounds(mapBounds);

    for (var i = 0, marker; marker = this.markers_[i]; i++) {
        if (!marker.isAdded && this.isMarkerInBounds_(marker, bounds)) {
            this.addToClosestCluster_(marker);
        }
    }
};


/**
 * A cluster that contains markers.
 *
 * @param {MarkerClusterer} markerClusterer The markerclusterer that this
 *     cluster is associated with.
 * @constructor
 * @ignore
 */
function Cluster(markerClusterer) {
    this.markerClusterer_ = markerClusterer;
    this.map_ = markerClusterer.getMap();
    this.gridSize_ = markerClusterer.getGridSize();
    this.minClusterSize_ = markerClusterer.getMinClusterSize();
    this.averageCenter_ = markerClusterer.isAverageCenter();
    this.center_ = null;
    this.markers_ = [];
    this.bounds_ = null;
    this.clusterIcon_ = new ClusterIcon(this, markerClusterer.getStyles(),
        markerClusterer.getGridSize());
}

/**
 * Determins if a marker is already added to the cluster.
 *
 * @param {google.maps.Marker} marker The marker to check.
 * @return {boolean} True if the marker is already added.
 */
Cluster.prototype.isMarkerAlreadyAdded = function(marker) {
    if (this.markers_.indexOf) {
        return this.markers_.indexOf(marker) != -1;
    } else {
        for (var i = 0, m; m = this.markers_[i]; i++) {
            if (m == marker) {
                return true;
            }
        }
    }
    return false;
};


/**
 * Add a marker the cluster.
 *
 * @param {google.maps.Marker} marker The marker to add.
 * @return {boolean} True if the marker was added.
 */
Cluster.prototype.addMarker = function(marker) {
    if (this.isMarkerAlreadyAdded(marker)) {
        return false;
    }

    if (!this.center_) {
        this.center_ = marker.getPosition();
        this.calculateBounds_();
    } else {
        if (this.averageCenter_) {
            var l = this.markers_.length + 1;
            var lat = (this.center_.lat() * (l - 1) + marker.getPosition().lat()) / l;
            var lng = (this.center_.lng() * (l - 1) + marker.getPosition().lng()) / l;
            this.center_ = new google.maps.LatLng(lat, lng);
            this.calculateBounds_();
        }
    }

    marker.isAdded = true;
    this.markers_.push(marker);

    var len = this.markers_.length;
    if (len < this.minClusterSize_ && marker.getMap() != this.map_) {
        // Min cluster size not reached so show the marker.
        marker.setMap(this.map_);
    }

    if (len == this.minClusterSize_) {
        // Hide the markers that were showing.
        for (var i = 0; i < len; i++) {
            this.markers_[i].setMap(null);
        }
    }

    if (len >= this.minClusterSize_) {
        marker.setMap(null);
    }

    this.updateIcon();
    return true;
};


/**
 * Returns the marker clusterer that the cluster is associated with.
 *
 * @return {MarkerClusterer} The associated marker clusterer.
 */
Cluster.prototype.getMarkerClusterer = function() {
    return this.markerClusterer_;
};


/**
 * Returns the bounds of the cluster.
 *
 * @return {google.maps.LatLngBounds} the cluster bounds.
 */
Cluster.prototype.getBounds = function() {
    var bounds = new google.maps.LatLngBounds(this.center_, this.center_);
    var markers = this.getMarkers();
    for (var i = 0, marker; marker = markers[i]; i++) {
        bounds.extend(marker.getPosition());
    }
    return bounds;
};


/**
 * Removes the cluster
 */
Cluster.prototype.remove = function() {
    this.clusterIcon_.remove();
    this.markers_.length = 0;
    delete this.markers_;
};


/**
 * Returns the number of markers in the cluster.
 *
 * @return {number} The number of markers in the cluster.
 */
Cluster.prototype.getSize = function() {
    return this.markers_.length;
};


/**
 * Returns a list of the markers in the cluster.
 *
 * @return {Array.<google.maps.Marker>} The markers in the cluster.
 */
Cluster.prototype.getMarkers = function() {
    return this.markers_;
};


/**
 * Returns the center of the cluster.
 *
 * @return {google.maps.LatLng} The cluster center.
 */
Cluster.prototype.getCenter = function() {
    return this.center_;
};


/**
 * Calculated the extended bounds of the cluster with the grid.
 *
 * @private
 */
Cluster.prototype.calculateBounds_ = function() {
    var bounds = new google.maps.LatLngBounds(this.center_, this.center_);
    this.bounds_ = this.markerClusterer_.getExtendedBounds(bounds);
};


/**
 * Determines if a marker lies in the clusters bounds.
 *
 * @param {google.maps.Marker} marker The marker to check.
 * @return {boolean} True if the marker lies in the bounds.
 */
Cluster.prototype.isMarkerInClusterBounds = function(marker) {
    return this.bounds_.contains(marker.getPosition());
};


/**
 * Returns the map that the cluster is associated with.
 *
 * @return {google.maps.Map} The map.
 */
Cluster.prototype.getMap = function() {
    return this.map_;
};


/**
 * Updates the cluster icon
 */
Cluster.prototype.updateIcon = function() {
    var zoom = this.map_.getZoom();
    var mz = this.markerClusterer_.getMaxZoom();

    if (mz && zoom > mz) {
        // The zoom is greater than our max zoom so show all the markers in cluster.
        for (var i = 0, marker; marker = this.markers_[i]; i++) {
            marker.setMap(this.map_);
        }
        return;
    }

    if (this.markers_.length < this.minClusterSize_) {
        // Min cluster size not yet reached.
        this.clusterIcon_.hide();
        return;
    }

    var numStyles = this.markerClusterer_.getStyles().length;
    var sums = this.markerClusterer_.getCalculator()(this.markers_, numStyles);
    this.clusterIcon_.setCenter(this.center_);
    this.clusterIcon_.setSums(sums);
    this.clusterIcon_.show();
};


/**
 * A cluster icon
 *
 * @param {Cluster} cluster The cluster to be associated with.
 * @param {Object} styles An object that has style properties:
 *     'url': (string) The image url.
 *     'height': (number) The image height.
 *     'width': (number) The image width.
 *     'anchor': (Array) The anchor position of the label text.
 *     'textColor': (string) The text color.
 *     'textSize': (number) The text size.
 *     'backgroundPosition: (string) The background postition x, y.
 * @param {number=} opt_padding Optional padding to apply to the cluster icon.
 * @constructor
 * @extends google.maps.OverlayView
 * @ignore
 */
function ClusterIcon(cluster, styles, opt_padding) {
    cluster.getMarkerClusterer().extend(ClusterIcon, google.maps.OverlayView);

    this.styles_ = styles;
    this.padding_ = opt_padding || 0;
    this.cluster_ = cluster;
    this.center_ = null;
    this.map_ = cluster.getMap();
    this.div_ = null;
    this.sums_ = null;
    this.visible_ = false;

    this.setMap(this.map_);
}


/**
 * Triggers the clusterclick event and zoom's if the option is set.
 */
ClusterIcon.prototype.triggerClusterClick = function() {
    var markerClusterer = this.cluster_.getMarkerClusterer();

    // Trigger the clusterclick event.
    google.maps.event.trigger(markerClusterer.map_, 'clusterclick', this.cluster_);

    if (markerClusterer.isZoomOnClick()) {
        // Zoom into the cluster.
        this.map_.fitBounds(this.cluster_.getBounds());
    }
};


/**
 * Adding the cluster icon to the dom.
 * @ignore
 */
ClusterIcon.prototype.onAdd = function() {
    this.div_ = document.createElement('DIV');
    if (this.visible_) {
        var pos = this.getPosFromLatLng_(this.center_);
        this.div_.style.cssText = this.createCss(pos);
        this.div_.innerHTML = this.sums_.text;
    }

    var panes = this.getPanes();
    panes.overlayMouseTarget.appendChild(this.div_);

    var that = this;
    google.maps.event.addDomListener(this.div_, 'click', function() {
        that.triggerClusterClick();
    });
};


/**
 * Returns the position to place the div dending on the latlng.
 *
 * @param {google.maps.LatLng} latlng The position in latlng.
 * @return {google.maps.Point} The position in pixels.
 * @private
 */
ClusterIcon.prototype.getPosFromLatLng_ = function(latlng) {
    var pos = this.getProjection().fromLatLngToDivPixel(latlng);
    pos.x -= parseInt(this.width_ / 2, 10);
    pos.y -= parseInt(this.height_ / 2, 10);
    return pos;
};


/**
 * Draw the icon.
 * @ignore
 */
ClusterIcon.prototype.draw = function() {
    if (this.visible_) {
        var pos = this.getPosFromLatLng_(this.center_);
        this.div_.style.top = pos.y + 'px';
        this.div_.style.left = pos.x + 'px';
    }
};


/**
 * Hide the icon.
 */
ClusterIcon.prototype.hide = function() {
    if (this.div_) {
        this.div_.style.display = 'none';
    }
    this.visible_ = false;
};


/**
 * Position and show the icon.
 */
ClusterIcon.prototype.show = function() {
    if (this.div_) {
        var pos = this.getPosFromLatLng_(this.center_);
        this.div_.style.cssText = this.createCss(pos);
        this.div_.style.display = '';
    }
    this.visible_ = true;
};


/**
 * Remove the icon from the map
 */
ClusterIcon.prototype.remove = function() {
    this.setMap(null);
};


/**
 * Implementation of the onRemove interface.
 * @ignore
 */
ClusterIcon.prototype.onRemove = function() {
    if (this.div_ && this.div_.parentNode) {
        this.hide();
        this.div_.parentNode.removeChild(this.div_);
        this.div_ = null;
    }
};


/**
 * Set the sums of the icon.
 *
 * @param {Object} sums The sums containing:
 *   'text': (string) The text to display in the icon.
 *   'index': (number) The style index of the icon.
 */
ClusterIcon.prototype.setSums = function(sums) {
    this.sums_ = sums;
    this.text_ = sums.text;
    this.index_ = sums.index;
    if (this.div_) {
        this.div_.innerHTML = sums.text;
    }

    this.useStyle();
};


/**
 * Sets the icon to the the styles.
 */
ClusterIcon.prototype.useStyle = function() {
    var index = Math.max(0, this.sums_.index - 1);
    index = Math.min(this.styles_.length - 1, index);
    var style = this.styles_[index];
    this.url_ = style['url'];
    this.height_ = style['height'];
    this.width_ = style['width'];
    this.textColor_ = style['textColor'];
    this.anchor_ = style['anchor'];
    this.textSize_ = style['textSize'];
    this.backgroundPosition_ = style['backgroundPosition'];
};


/**
 * Sets the center of the icon.
 *
 * @param {google.maps.LatLng} center The latlng to set as the center.
 */
ClusterIcon.prototype.setCenter = function(center) {
    this.center_ = center;
};


/**
 * Create the css text based on the position of the icon.
 *
 * @param {google.maps.Point} pos The position.
 * @return {string} The css style text.
 */
ClusterIcon.prototype.createCss = function(pos) {
    var style = [];
    style.push('background-size:contain;background-repeat:no-repeat;background-image:url(' + this.url_ + ');');
    var backgroundPosition = this.backgroundPosition_ ? this.backgroundPosition_ : '0 0';
    style.push('background-position:' + backgroundPosition + ';');

    if (typeof this.anchor_ === 'object') {
        if (typeof this.anchor_[0] === 'number' && this.anchor_[0] > 0 &&
            this.anchor_[0] < this.height_) {
            style.push('height:' + (this.height_ - this.anchor_[0]) +
                'px; padding-top:' + this.anchor_[0] + 'px;');
        } else {
            style.push('height:' + this.height_ + 'px; line-height:' + this.height_ +
                'px;');
        }
        if (typeof this.anchor_[1] === 'number' && this.anchor_[1] > 0 &&
            this.anchor_[1] < this.width_) {
            style.push('width:' + (this.width_ - this.anchor_[1]) +
                'px; padding-left:' + this.anchor_[1] + 'px;');
        } else {
            style.push('width:' + this.width_ + 'px; text-align:center;');
        }
    } else {
        style.push('height:' + this.height_ + 'px; line-height:' +
            this.height_ + 'px; width:' + this.width_ + 'px; text-align:center;');
    }

    var txtColor = this.textColor_ ? this.textColor_ : 'black';
    var txtSize = this.textSize_ ? this.textSize_ : 11;

    style.push('cursor:pointer; top:' + pos.y + 'px; left:' +
        pos.x + 'px; color:' + txtColor + '; position:absolute; font-size:' +
        txtSize + 'px; font-family:Arial,sans-serif; font-weight:bold');
    return style.join('');
};


// Export Symbols for Closure
// If you are not going to compile with closure then you can remove the
// code below.
window['MarkerClusterer'] = MarkerClusterer;
MarkerClusterer.prototype['addMarker'] = MarkerClusterer.prototype.addMarker;
MarkerClusterer.prototype['addMarkers'] = MarkerClusterer.prototype.addMarkers;
MarkerClusterer.prototype['clearMarkers'] =
    MarkerClusterer.prototype.clearMarkers;
MarkerClusterer.prototype['fitMapToMarkers'] =
    MarkerClusterer.prototype.fitMapToMarkers;
MarkerClusterer.prototype['getCalculator'] =
    MarkerClusterer.prototype.getCalculator;
MarkerClusterer.prototype['getGridSize'] =
    MarkerClusterer.prototype.getGridSize;
MarkerClusterer.prototype['getExtendedBounds'] =
    MarkerClusterer.prototype.getExtendedBounds;
MarkerClusterer.prototype['getMap'] = MarkerClusterer.prototype.getMap;
MarkerClusterer.prototype['getMarkers'] = MarkerClusterer.prototype.getMarkers;
MarkerClusterer.prototype['getMaxZoom'] = MarkerClusterer.prototype.getMaxZoom;
MarkerClusterer.prototype['getStyles'] = MarkerClusterer.prototype.getStyles;
MarkerClusterer.prototype['getTotalClusters'] =
    MarkerClusterer.prototype.getTotalClusters;
MarkerClusterer.prototype['getTotalMarkers'] =
    MarkerClusterer.prototype.getTotalMarkers;
MarkerClusterer.prototype['redraw'] = MarkerClusterer.prototype.redraw;
MarkerClusterer.prototype['removeMarker'] =
    MarkerClusterer.prototype.removeMarker;
MarkerClusterer.prototype['removeMarkers'] =
    MarkerClusterer.prototype.removeMarkers;
MarkerClusterer.prototype['resetViewport'] =
    MarkerClusterer.prototype.resetViewport;
MarkerClusterer.prototype['repaint'] =
    MarkerClusterer.prototype.repaint;
MarkerClusterer.prototype['setCalculator'] =
    MarkerClusterer.prototype.setCalculator;
MarkerClusterer.prototype['setGridSize'] =
    MarkerClusterer.prototype.setGridSize;
MarkerClusterer.prototype['setMaxZoom'] =
    MarkerClusterer.prototype.setMaxZoom;
MarkerClusterer.prototype['onAdd'] = MarkerClusterer.prototype.onAdd;
MarkerClusterer.prototype['draw'] = MarkerClusterer.prototype.draw;

Cluster.prototype['getCenter'] = Cluster.prototype.getCenter;
Cluster.prototype['getSize'] = Cluster.prototype.getSize;
Cluster.prototype['getMarkers'] = Cluster.prototype.getMarkers;

ClusterIcon.prototype['onAdd'] = ClusterIcon.prototype.onAdd;
ClusterIcon.prototype['draw'] = ClusterIcon.prototype.draw;
ClusterIcon.prototype['onRemove'] = ClusterIcon.prototype.onRemove;

Object.keys = Object.keys || function(o) {
    var result = [];
    for (var name in o) {
        if (o.hasOwnProperty(name))
            result.push(name);
    }
    return result;
};


var locations = [
  {name:'taipei101',price:'350',lat:25.0339031,lng:121.5623212},
  {name:'airport',price:'150',lat:25.063236,lng:121.5503405},
  {name:'train station',price:'160',lat:25.0455016,lng:121.5186618},
  {name:'MRT station',price:'100',lat:25.0625538,lng:121.5171593}, 
  {name:'aaa station',price:'100',lat:25.062236,lng:121.554405}, 
  {name:'bbb station',price:'300',lat:25.0685538,lng:121.5151593}, 
  {name:'ccc station',price:'400',lat:25.066236,lng:121.555405}, 
  {name:'ddd station',price:'500',lat:25.056236,lng:121.555405}, 
  {name:'eee station',price:'500',lat:25.056236,lng:121.535405}, 
  {name:'fff station',price:'600',lat:25.054236,lng:121.545405}, 
  {name:'ggg station',price:'700',lat:25.055236,lng:121.546405}, 
  {name:'ggg station',price:'700',lat:25.054236,lng:121.546705}, 
];

var imgArr =   [{
    url: 'https://raw.githubusercontent.com/googlemaps/v3-utility-library/master/markerclusterer/images/conv40.png',
    height: 55,
    width: 90,
    anchor: [6, 0],
    textColor: '#fff',
    textSize: 10,
    backgroundPosition:'center',
}];


function initialize() {
  var markerCenter = new google.maps.LatLng(25.0625938,121.5288613);
  var mapOptions = {
    zoom: 13,
    center: markerCenter,
  };
  map = new google.maps.Map(document.getElementById('map'),
          mapOptions);
  marker = new google.maps.Marker({
    map:map,
    animation: google.maps.Animation.DROP,
		position: markerCenter
  });
  var markersArr = [];
    for (var i = 0; i < locations.length; i++) {
          var item = locations[i];
          var infowindow = new google.maps.InfoWindow();
          var marker = new MarkerWithLabel({
                    draggable: false,
                    raiseOnDrag: false,
                    icon: ' ',
                    map: map,
                    labelContent: '<span>'+ item.name +'<br/>NT'+ item.price +'</span>',
                    labelAnchor: new google.maps.Point(40,32),
                    labelClass: "labels", // the CSS class for the label
                    labelStyle: {opacity: 1},
                    position: {lat: item.lat, lng: item.lng},
                    data:'Go to '+item.name + '<br/> Taxi price: NT' +item.price,
                    dataPrice: item.price
          });
        markersArr.push(marker);
        marker.addListener('click', function() {
          infowindow.setContent( this.data );
          infowindow.open(map, this);
        });
     }
createGroup(markersArr)
}
google.maps.event.addDomListener(window, 'load', initialize);
function createGroup(arr){
  markerCluster = new MarkerClusterer(map, arr, {
    gridSize: 50, 
    maxZoom: 15,
    zoomOnClick: true,
    styles: imgArr,
    imagePath: 'https://googlemaps.github.io/js-marker-clusterer/images/m'
  });
  // 上方 library 直接拉近 event失效
	// google.maps.event.addListener(markerCluster, 'clusterclick', function(cluster) {
	// 	var markers = cluster.getMarkers();
	// var string = '';
	// 	for(var i = 0; i < markers.length; i++) {
	// 		string += markers[i].data.replace('<br/>','') +'\n';
	// 	}
	// alert(string);
	// });
}
              
            
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999px

Console