Pen Settings



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. You can use the CSS from another Pen by using it's URL and the proper URL extention.

+ add another resource


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


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.


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.


                <h1>Switchin' It Up</h1>
    <select id="js-select-endpoint">
      <option value="users">Users</option>
      <option value="posts">Posts</option>

    <select id="js-select-id">
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
      <option value="4">4</option>
      <option value="5">5</option>
      <option value="6">6</option>
      <option value="7">7</option>
      <option value="8">8</option>
    <pre id="js-response-box">


                table {
  padding: 14px;


                'use strict';

// Helper Method
const ENDPOINT = 'users',
    ROOT     = '';

const makeRequest = function makeRequest(path, item) {
return new Promise(function(resolve, reject) {
  // Assumes jQuery
  path ? (path = '/' + path) : path = '/';
  item ? (item = '/' + item) : item = '/';
  const url = ROOT + path + item;
    .done(function (data) {
    .fail(function () {
// Code goes here
const select    = document.getElementById('js-select-endpoint'),
    id_select = document.getElementById('js-select-id'),
    response_box = document.getElementById('js-response-box');

// STREAM of button clicks on ENDPOINT selection
const endpoint_stream = 
  Rx.Observable.fromEvent(select, 'click').
    map(event  =>
    map(target => (target.options[target.selectedIndex].text.toLowerCase()));

const id_stream = 
  Rx.Observable.fromEvent(id_select, 'click').
    map(event  =>
    map(target => target.options[target.selectedIndex].text.toLowerCase());
const request_stream  = 
  // To wait until BOTH fields get updated, use zip:
    // Emits ARRAY: First element is from endpoint_stream, second is from id_stream
    map(data => makeRequest(data[0], data[1]))
    // Only hit server for DIFFERENT requests
    .subscribe(response => {
      response_box.innerHTML = JSON.stringify(response, null, 2);