如何向元素添加onload事件?
我可以使用:
<div onload="oQuickReply.swap();" ></div>
对于这个吗?
如何向元素添加onload事件?
我可以使用:
<div onload="oQuickReply.swap();" ></div>
对于这个吗?
当前回答
不,你不能。使其工作的最简单的方法是将函数调用直接放在元素之后
例子:
...
<div id="somid">Some content</div>
<script type="text/javascript">
oQuickReply.swap('somid');
</script>
...
或者-甚至更好-就在</body>前面:
...
<script type="text/javascript">
oQuickReply.swap('somid');
</script>
</body>
...因此它不会阻止以下内容的加载。
其他回答
不,你不能。使其工作的最简单的方法是将函数调用直接放在元素之后
例子:
...
<div id="somid">Some content</div>
<script type="text/javascript">
oQuickReply.swap('somid');
</script>
...
或者-甚至更好-就在</body>前面:
...
<script type="text/javascript">
oQuickReply.swap('somid');
</script>
</body>
...因此它不会阻止以下内容的加载。
利用身体。通过属性(<body onload="myFn()“>…”)或者用Javascript绑定一个事件。这在jQuery中非常常见:
$(document).ready(function() {
doSomething($('#myDiv'));
});
您可以如下所示附加一个事件侦听器。当选择器#my-id的div完全加载到DOM时,它就会触发。
$(document).on('EventName', '#my-id', function() {
// do something
});
在本例中,EventName可以是'load'或'click'
https://api.jquery.com/on/#on-events-selector-data-handler
由于onload事件仅在少数元素上受支持,因此必须使用另一种方法。
你可以使用MutationObserver:
const trackElement = element => { let present = false; const checkIfPresent = () => { if (document.body.contains(element)) { if (!present) { console.log('in DOM:', element); } present = true; } else if (present) { present = false; console.log('Not in DOM'); } }; const observer = new MutationObserver(checkIfPresent); observer.observe(document.body, { childList: true }); checkIfPresent(); return observer; }; const element = document.querySelector('#element'); const add = () => document.body.appendChild(element); const remove = () => element.remove(); trackElement(element); <button onclick="add()">Add</button> <button onclick="remove()">Remove</button> <div id="element">Element</div>
避免使用任何基于间隔的方法(因为它们不是性能和准确的),并使用MutationObserver针对动态加载div的父div以获得更好的效率。
更新:这是我写的一个方便的函数。像这样使用它:
onElementLoaded("div.some_class").then(()=>{}).catch(()=>{});
/**
*
* Wait for an HTML element to be loaded like `div`, `span`, `img`, etc.
* ex: `onElementLoaded("div.some_class").then(()=>{}).catch(()=>{})`
* @param {*} elementToObserve wait for this element to load
* @param {*} parentStaticElement (optional) if parent element is not passed then `document` is used
* @return {*} Promise - return promise when `elementToObserve` is loaded
*/
function onElementLoaded(elementToObserve, parentStaticElement) {
const promise = new Promise((resolve, reject) => {
try {
if (document.querySelector(elementToObserve)) {
console.log(`element already present: ${elementToObserve}`);
resolve(true);
return;
}
const parentElement = parentStaticElement
? document.querySelector(parentStaticElement)
: document;
const observer = new MutationObserver((mutationList, obsrvr) => {
const divToCheck = document.querySelector(elementToObserve);
if (divToCheck) {
console.log(`element loaded: ${elementToObserve}`);
obsrvr.disconnect(); // stop observing
resolve(true);
}
});
// start observing for dynamic div
observer.observe(parentElement, {
childList: true,
subtree: true,
});
} catch (e) {
console.log(e);
reject(Error("some issue... promise rejected"));
}
});
return promise;
}
实现细节:
HTML:
<div class="parent-static-div">
<div class="dynamic-loaded-div">
this div is loaded after DOM ready event
</div>
</div>
JS:
var observer = new MutationObserver(function (mutationList, obsrvr) {
var div_to_check = document.querySelector(".dynamic-loaded-div"); //get div by class
// var div_to_check = document.getElementById('div-id'); //get div by id
console.log("checking for div...");
if (div_to_check) {
console.log("div is loaded now"); // DO YOUR STUFF!
obsrvr.disconnect(); // stop observing
return;
}
});
var parentElement = document.querySelector("parent-static-div"); // use parent div which is already present in DOM to maximise efficiency
// var parentElement = document // if not sure about parent div then just use whole 'document'
// start observing for dynamic div
observer.observe(parentElement, {
// for properties details: https://developer.mozilla.org/en-US/docs/Web/API/MutationObserverInit
childList: true,
subtree: true,
});