js监听某个元素高度变化来改变父级iframe的高度
最近需要做一个iframe调用其他页面内容，这个iframe地址是可变化的，但是里面的内容高度不确定且里面内容高度可调整，所以需要通过监听iframe里面body的高度变化来调整iframe的高度。
后面发现了一个好用的插件detect-element-resize.js，首先看一下这个插件的介绍：
插件简介
跨浏览器，基于事件，元素调整大小检测。
简而言之，此实现不使用内部计时器来检测大小更改（就像我发现的大多数实现一样）。它使用scroll大多数浏览器上的onresize事件，以及IE10及以下的事件。
使用的方法不仅检测javascript生成的调整大小更改，还检测CSS伪类的更改，例如：hover，CSS动画等。
插件兼容性
Chrome
Firefox
IE 11 及以下 (在11,10,9,8和7上测试)
已知问题
在IE 10及更低版本上：如果分离元素并重新附加它，则需要再次添加调整大小侦听器。
源代码
(function () {
var attachEvent = document.attachEvent,
stylesCreated = false;
if (!attachEvent) {
var requestFrame = (function(){
var raf = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame ||
function(fn){ return window.setTimeout(fn, 20); };
return function(fn){ return raf(fn); };
})();
var cancelFrame = (function(){
var cancel = window.cancelAnimationFrame || window.mozCancelAnimationFrame || window.webkitCancelAnimationFrame ||
window.clearTimeout;
return function(id){ return cancel(id); };
})();
function resetTriggers(element){
var triggers = element.__resizeTriggers__,
expand = triggers.firstElementChild,
contract = triggers.lastElementChild,
expandChild = expand.firstElementChild;
contract.scrollLeft = contract.scrollWidth;
contract.scrollTop = contract.scrollHeight;
expandChild.style.width = expand.offsetWidth + 1 + 'px';
expandChild.style.height = expand.offsetHeight + 1 + 'px';
expand.scrollLeft = expand.scrollWidth;
expand.scrollTop = expand.scrollHeight;
};
function checkTriggers(element){
return element.offsetWidth != element.__resizeLast__.width ||
element.offsetHeight != element.__resizeLast__.height;
}
function scrollListener(e){
var element = this;
resetTriggers(this);
if (this.__resizeRAF__) cancelFrame(this.__resizeRAF__);
this.__resizeRAF__ = requestFrame(function(){
if (checkTriggers(element)) {
element.__resizeLast__.width = element.offsetWidth;
element.__resizeLast__.height = element.offsetHeight;
element.__resizeListeners__.forEach(function(fn){
fn.call(element, e);
});
}
});
};
/* Detect CSS Animations support to detect element display/re-attach */
var animation = false,
animationstring = 'animation',
keyframeprefix = '',
animationstartevent = 'animationstart',
domPrefixes = 'Webkit Moz O ms'.split(' '),
startEvents = 'webkitAnimationStart animationstart oAnimationStart MSAnimationStart'.split(' '),
pfx = '';
{
var elm = document.createElement('fakeelement');
if( elm.style.animationName !== undefined ) { animation = true; }
if( animation === false ) {
for( var i = 0; i < domPrefixes.length; i++ ) {
if( elm.style[ domPrefixes[i] + 'AnimationName' ] !== undefined ) {
pfx = domPrefixes[ i ];
animationstring = pfx + 'Animation';
keyframeprefix = '-' + pfx.toLowerCase() + '-';
animationstartevent = startEvents[ i ];
animation = true;
break;
}
}
}
}
var animationName = 'resizeanim';
var animationKeyframes = '@' + keyframeprefix + 'keyframes ' + animationName + ' { from { opacity: 0; } to { opacity: 0; } } ';
var animationStyle = keyframeprefix + 'animation: 1ms ' + animationName + '; ';
}
function createStyles() {
if (!stylesCreated) {
//opacity:0 works around a chrome bug https://code.google.com/p/chromium/issues/detail?id=286360
var css = (animationKeyframes ? animationKeyframes : '') +
'.resize-triggers { ' + (animationStyle ? animationStyle : '') + 'visibility: hidden; opacity: 0; } ' +
'.resize-triggers, .resize-triggers > div, .contract-trigger:before { content: \" \"; display: block; position: absolute; top: 0; left: 0; height: 100%; width: 100%; overflow: hidden; } .resize-triggers > div { background: #eee; overflow: auto; } .contract-trigger:before { width: 200%; height: 200%; }',
head = document.head || document.getElementsByTagName('head')[0],
style = document.createElement('style');
style.type = 'text/css';
if (style.styleSheet) {
style.styleSheet.cssText = css;
} else {
style.appendChild(document.createTextNode(css));
}
head.appendChild(style);
stylesCreated = true;
}
}
window.addResizeListener = function(element, fn){
if (attachEvent) element.attachEvent('onresize', fn);
else {
if (!element.__resizeTriggers__) {
if (getComputedStyle(element).position == 'static') element.style.position = 'relative';
createStyles();
element.__resizeLast__ = {};
element.__resizeListeners__ = [];
(element.__resizeTriggers__ = document.createElement('div')).className = 'resize-triggers';
element.__resizeTriggers__.innerHTML = '<div class="expand-trigger"><div></div></div>' +
'<div class="contract-trigger"></div>';
element.appendChild(element.__resizeTriggers__);
resetTriggers(element);
element.addEventListener('scroll', scrollListener, true);
/* Listen for a css animation to detect element display/re-attach */
animationstartevent && element.__resizeTriggers__.addEventListener(animationstartevent, function(e) {
if(e.animationName == animationName)
resetTriggers(element);
});
}
element.__resizeListeners__.push(fn);
}
};
window.removeResizeListener = function(element, fn){
if (attachEvent) element.detachEvent('onresize', fn);
else {
element.__resizeListeners__.splice(element.__resizeListeners__.indexOf(fn), 1);
if (!element.__resizeListeners__.length) {
element.removeEventListener('scroll', scrollListener);
element.__resizeTriggers__ = !element.removeChild(element.__resizeTriggers__);
}
}
}
})();
调用方法
addResizeListener(element,fun) //element为监听的元素，fun为当有变化时触发的方法
//例如监听body的高度变化：
addResizeListener(document.getElementsByTagName("body")[0],detectCallback);
var detectCallback = function() {
console.log('页面body高度发生了变化')
};
实例：
监听iframe页面变化时iframe的高度等于iframe里面页面body的高度
<iframe src="url" frameborder="0" id="container"></iframe>
//iframe 页面代码
window.onload=function(){
setParentIframeHeight('container');
addResizeListener(document.getElementsByTagName("body")[0], detectCallback);
}
var detectCallback = function() {
setParentIframeHeight('container');
};
function setParentIframeHeight(id){
var parentIframe = parent.document.getElementById(id);
parentIframe.height = document.body.scrollHeight;
}
detect-element-resize.js插件地址：https://github.com/sdecima/javascript-detect-element-resize
