platinum-sw-import-script.html

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<link rel="import" href="../polymer/polymer.html">

<script>
  /**
   * The `<platinum-sw-import-script>` element is used to import a JavaScript file
   * that is executed each time the service worker starts up.
   *
   * `<platinum-sw-import-script>` needs to be a child element of
   * `<platinum-sw-register>`.
   *
   * A common use case is to define a custom request handler for a `fetch` event,
   * but it can be used for any type of code that you want to be executed by the
   * service worker.
   *
   *     <platinum-sw-register auto-register>
   *       <platinum-sw-import-script
   * href="custom-fetch-handler.js"></platinum-sw-import-script>
   *       <platinum-sw-fetch handler="customFetchHandler"
   *                          path="/(.*)/customFetch"></platinum-sw-fetch>
   *     </platinum-sw-register>
   *
   * You can specify multiple `<platinum-sw-import-script>` elements, each one
   * corresponding to a different JavaScript file. The JavaScript files will be
   * loaded in the order in which the
   * `<platinum-sw-import-script>` elements appear. Under the hood, this results
   * in an
   * [`importScripts()`](https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/importScripts)
   * call made from the context of the service worker.
   */
  Polymer({
    is: 'platinum-sw-import-script',

    properties: {
      /**
       * The URL of the JavaScript file that you want imported.
       *
       * Relative URLs are assumed to be
       * relative to the service worker's script location, which will almost
       * always be the same location as the page which includes this element.
       */
      href: String
    },

    _getParameters: function() {
      return new Promise(function(resolve) {
        var params = {};
        if (this.href) {
          params.importscript = this.href;
        } else {
          Polymer.Base._warn(
              'The following platinum-sw-import-script element will not have any effect.' +
                  ' The "href" attribute must be set.',
              this);
        }
        resolve(params);
      }.bind(this));
    }
  });
</script>