@polymer/polymer/lib/utils/telemetry.html

The Polymer library makes it easy to create your own web components. Give your element some markup and properties, and then use it on a site. Polymer provides features like dynamic templates and data binding to reduce the amount of boilerplate you need to

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<link rel="import" href="boot.html">
<script>
(function() {
  'use strict';

  /**
   * Provides basic tracking of element definitions (registrations) and
   * instance counts.
   *
   * @namespace
   * @summary Provides basic tracking of element definitions (registrations) and
   * instance counts.
   */
  Polymer.telemetry = {
    /**
     * Total number of Polymer element instances created.
     * @type {number}
     */
    instanceCount: 0,
    /**
     * Array of Polymer element classes that have been finalized.
     * @type {Array<Polymer.Element>}
     */
    registrations: [],
    /**
     * @param {!PolymerElementConstructor} prototype Element prototype to log
     * @this {this}
     * @private
     */
    _regLog: function(prototype) {
      console.log('[' + prototype.is + ']: registered');
    },
    /**
     * Registers a class prototype for telemetry purposes.
     * @param {HTMLElement} prototype Element prototype to register
     * @this {this}
     * @protected
     */
    register: function(prototype) {
      this.registrations.push(prototype);
      Polymer.log && this._regLog(prototype);
    },
    /**
     * Logs all elements registered with an `is` to the console.
     * @public
     * @this {this}
     */
    dumpRegistrations: function() {
      this.registrations.forEach(this._regLog);
    }
  };

})();
</script>