text: // COPYRIGHT © 2018 Esri
  //
  // All rights reserved under the copyright laws of the United States
  // and applicable international laws, treaties, and conventions.
  //
  // This material is licensed for use under the Esri Master License
  // Agreement (MLA), and is bound by the terms of that agreement.
  // You may redistribute and use this code without modification,
  // provided you adhere to the terms of the MLA and include this
  // copyright notice.
  //
  // See use restrictions at http://www.esri.com/legal/pdfs/mla_e204_e300/english
  //
  // For additional information, contact:
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  // Attn: Contracts and Legal Services Department
  // 380 New York Street
  // Redlands, California, USA 92373
  // USA
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  //
  // See http://js.arcgis.com/4.10/esri/copyright.txt for details.
  
  define(["require","exports"],function(e,t){Object.defineProperty(t,"__esModule",{value:!0});var n=function(){function e(){this._listeners={}}return e.prototype.on=function(e,t){var n=this;null==this._listeners[e]&&(this._listeners[e]=new Map);var r={};return this._listeners[e].set(r,t),{remove:function(){return n._listeners[e].delete(r)}}},e.prototype.once=function(e,t){var n=this.on(e,function(e){n.remove(),t(e)});return n},e.prototype.emit=function(e,t){this.hasEventListener(e)&&this._listeners[e].forEach(function(e){return e(t)})},e.prototype.hasEventListener=function(e){return null!=this._listeners[e]&&this._listeners[e].size>0},e}();t.default=n});