JS monitors the width and height changes of div

Preface explains

1. Monitoring will be encountered during development div The width and height of . For example, when the width and height change echarts Need to redraw .
2. Realization principle ： hold div Put it in iframe in , monitor iframe Of resize event .

vue call

import {ElementResize} from '@/utils/ElementResize.js
// Create a listening instance 
var eleResize = new ElementResize('#content');
  eleResize.listen(function() {
  console.log(' monitor ')
})

monitor ElementResize.js file

/**
   *  Element width height monitoring 
   * @param {Object} el  Listen for element selectors 
   */
  function ElementResize(eleSelector) {
   if (!(this instanceof ElementResize)) return;
   if (!eleSelector) return;
   this.eleSelector = eleSelector;
   this.el = document.querySelector(eleSelector);
   this.queue = [];
   this.__init(); //globel init
  }
 
  // initialization 
  ElementResize.prototype.__init = function() {
   let iframe = this.crateIElement();
   this.el.style.position = 'relative';
   this.el.appendChild(iframe)
   this.bindEvent(iframe.contentWindow);
  }
 
  /**
   *  Set element style 
   * @param {HTMLObject} el
   * @param {Object} styleJson
   */
  ElementResize.prototype.setStyle = function(el, styleJson) {
   if (!el) return;
   styleJson = styleJson || {
   opacity: 0,
   'z-index': '-1111',
   position: 'absolute',
   left: 0,
   top: 0,
   width: '100%',
   height: '100%',
   };
   let styleText = '';
   for (var key in styleJson) {
   styleText += (key + ':' + styleJson[key] + ';');
   }
   el.style.cssText = styleText;
  }
 
  /**
   *  Create elements 
   * @param {Object} style
   */
  ElementResize.prototype.crateIElement = function(style) {
   let iframe = document.createElement('iframe');
   this.setStyle(iframe);
   return iframe;
  }
 
  /**
   *  The binding event 
   * @param {Object} el
   */
  ElementResize.prototype.bindEvent = function(el) {
   if (!el) return;
   var _self = this;
   el.addEventListener('resize', function() {
   _self.runQueue();
   }, false)
  }
 
  /**
   *  Run the queue 
   */
  ElementResize.prototype.runQueue = function() {
   let queue = this.queue;
   for (var i = 0; i < queue.length; i++) {
   (typeof queue[i]) === 'function' && queue[i].apply(this);
   }
  }
 
  /**
   *  External monitoring 
   * @param {Object} cb  Callback function 
   */
  ElementResize.prototype.listen = function(cb) {
   if (typeof cb !== 'function') throw new TypeError('cb is not a function!');
   this.queue.push(cb);
  }