JS如何监听div的resize事件

开发过程中经常遇到的一个问题就是如何监听一个div的size变化。比如我用canvas绘制了一个chart，当canvas的size发生变化的时候，需要重新绘制里面的内容，这个时候就需要监听resize事件做处理。window上虽然可以添加resize事件监听，但这并不能满足我们的需求，因为很多时候，div的size发生了变化，但是window的size并没有改变。不过我们可以间接利用window的resize事件监听来实现对于某个div的resize事件监听，请看下面具体实现。对于div的resize事件的监听，实现方式有很多，比如周期性检查，通过scroll事件等等，本文主要介绍通过object元素来实现监听。具体实现：

// EleResize.js
var EleResize = {
 _handleResize: function (e) {
  var ele = e.target || e.srcElement;
  var trigger = ele.__resizeTrigger__;
  if (trigger) {
   var handlers = trigger.__z_resizeListeners;
   if (handlers) {
    var size = handlers.length;
    for (var i = 0; i < size; i++) {
     var h = handlers[i];
     var handler = h.handler;
     var context = h.context;
     handler.apply(context, [e]);
    }
   }
  }
 },
 _removeHandler: function (ele, handler, context) {
  var handlers = ele.__z_resizeListeners;
  if (handlers) {
   var size = handlers.length;
   for (var i = 0; i < size; i++) {
    var h = handlers[i];
    if (h.handler === handler && h.context === context) {
     handlers.splice(i, 1);
     return;
    }
   }
  }
 },
 _createResizeTrigger: function (ele) {
  var obj = document.createElement('object');
  obj.setAttribute('style',
   'display: block; position: absolute; top: 0; left: 0; height: 100%; width: 100%; overflow: hidden;opacity: 0; pointer-events: none; z-index: -1;');
  obj.onload = EleResize._handleObjectLoad;
  obj.type = 'text/html';
  ele.appendChild(obj);
  obj.data = 'about:blank';
  return obj;
 },
 _handleObjectLoad: function (evt) {
  this.contentDocument.defaultView.__resizeTrigger__ = this.__resizeElement__;
  this.contentDocument.defaultView.addEventListener('resize', EleResize._handleResize);
 }
};
if (document.attachEvent) {//ie9-10
 EleResize.on = function (ele, handler, context) {
  var handlers = ele.__z_resizeListeners;
  if (!handlers) {
   handlers = [];
   ele.__z_resizeListeners = handlers;
   ele.__resizeTrigger__ = ele;
   ele.attachEvent('onresize', EleResize._handleResize);
  }
  handlers.push({
   handler: handler,
   context: context
  });
 };
 EleResize.off = function (ele, handler, context) {
  var handlers = ele.__z_resizeListeners;
  if (handlers) {
   EleResize._removeHandler(ele, handler, context);
   if (handlers.length === 0) {
    ele.detachEvent('onresize', EleResize._handleResize);
    delete ele.__z_resizeListeners;
   }
  }
 }
} else {
 EleResize.on = function (ele, handler, context) {
  var handlers = ele.__z_resizeListeners;
  if (!handlers) {
   handlers = [];
   ele.__z_resizeListeners = handlers;

   if (getComputedStyle(ele, null).position === 'static') {
    ele.style.position = 'relative';
   }
   var obj = EleResize._createResizeTrigger(ele);
   ele.__resizeTrigger__ = obj;
   obj.__resizeElement__ = ele;
  }
  handlers.push({
   handler: handler,
   context: context
  });
 };
 EleResize.off = function (ele, handler, context) {
  var handlers = ele.__z_resizeListeners;
  if (handlers) {
   EleResize._removeHandler(ele, handler, context);
   if (handlers.length === 0) {
    var trigger = ele.__resizeTrigger__;
    if (trigger) {
     trigger.contentDocument.defaultView.removeEventListener('resize', EleResize._handleResize);
     ele.removeChild(trigger);
     delete ele.__resizeTrigger__;
    }
    delete ele.__z_resizeListeners;
   }
  }
 }
}

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测试代码

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Resize</title>
 <script src="./EleResize.js"></script>
 <style>
  html, body {
   margin: 0;
   padding: 0;
   width: 100%;
   height: 100%;
  }

  #resizeDiv {
   width: 60%;
   height: 60%;
   border: 1px solid red;
   margin: 20px;
  }

  button {
   margin: 20px 20px 0;
  }
 </style>
</head>
<body>
<button onclick="addListener()">addListener</button>
<button onclick="removeListener()">removeListener</button>
<button onclick="resize()">resize</button>
<div id="resizeDiv"></div>
<script>
 var resizeDiv = document.getElementById('resizeDiv');
 function resize() {
  resizeDiv.style.width = "200px";
 }
 var listener = function () {
  console.log("resize");
 };
 function addListener() {
  EleResize.on(resizeDiv, listener);
 }
 function removeListener() {
  EleResize.off(resizeDiv, listener)
 }
</script>
</body>
</html>

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#JavaScript

上次更新: 2024/01/30, 00:35:17

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