Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                
<h2>The person below will change in <span id='timer'>5</span> seconds</h2>
<!-- 下面是 mvvm 中的 View层 -->
<!-- View层 start -->
<div>Name: <span id="name">Nelson Kuang</span></div>
<div>Age: <span id="age">18</span></div>
<!-- View层 end -->
              
            
!

CSS

              
                
              
            
!

JS

              
                // --- View层 请看Html代码段
// --------- Model层 ----------
var newPerson = {
  name: 'Nelson Kuang',
  age: 18
};

// --------- viewModel层 ----------
Object.defineProperty(newPerson, 'name', {
    set: function (x) {
        if (x !== this.oldPropValue) {
            document.querySelector('#name').innerHTML = x
            this.oldPropValue = x;
        } else {
            console.log('name的值没变')
        }
    },
    get: function () {
        console.log('in property get accessor');
        return this.oldPropValue;
    },
    enumerable: true,
    configurable: true
});
Object.defineProperty(newPerson, 'age', {
    set: function (x) {
        if (x !== this.oldPropValue) {
            document.querySelector('#age').innerHTML = x
            this.oldPropValue = x;
        } else {
            console.log('age的值没变')
        }
    },
    get: function () {
        console.log('in property get accessor');
        return this.oldPropValue;
    },
    enumerable: true,
    configurable: true
});
// --------- mvvm 数据驱动开发方式,现在只需修改newPerson的数据,View层的Dom节点会自动更新,如下:
  setTimeout(function(){
    // mvvm 数据驱动开发方式
    newPerson.name = 'Gary Li'
    newPerson.age = 20
  }, 5000)


// 下面只是计时器,与上面无关,set the timer
Object.prototype.delay = function (time, doSomething) {
    var self = this,
        startTime = time;
    if (self) {
        setTimeout(function () {
            doSomething(self, startTime);
        }, time);
    }
    return this;
}
var el = document.querySelector('#timer');
for (var i = 0; i <= 5; i++) {
    el.delay(i * 1000, function (self, startTime) {
        self.innerHTML = 5 - startTime / 1000;
    })
}
              
            
!
999px

Console