[英]Can't access DOM element
I wrote a web application with a body onload event. 我编写了带有body onload事件的Web应用程序。 I know this isn't optimal so I want to use DOMContentLoaded to trigger my init event.
我知道这不是最佳选择,所以我想使用DOMContentLoaded触发我的init事件。
I have a strange problem, I can't access my DOM element and I don't know why :/. 我有一个奇怪的问题,我无法访问DOM元素,也不知道为什么:/。
HTML: HTML:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<script type="text/javascript" src="main.js"></script>
</head>
<body>
<div id="test">Hello World</div>
</body>
</html>
JS: JS:
// add event listener
document.addEventListener('DOMContentLoaded', init, false);
function init () {
// pop up
alert(document.getElementById(test).innerHTML);
}
Does somebody see the problem? 有人看到问题了吗?
You are passing the undefined variable test
to the getElementById()
function, instead of the string value 'test'
. 您要将未定义的变量
test
传递给getElementById()
函数,而不是字符串值'test'
。
So 所以
document.getElementById(test); // Incorrect - as an undefined varible
Should in fact be 实际上应该是
document.getElementById('test') // Correct - as a string value
Or 要么
var element_id = 'test';
document.getElementById(element_id) // Correct - as a defined variable
Add double quotes around test ie "test" 在测试周围添加双引号,即“ test”
document.addEventListener('DOMContentLoaded', init, false);
function init () {
// pop up
alert(document.getElementById("test").innerHTML);
}
If your init function is executed, then you might add quote arroud your id : 如果执行了init函数,则可以在id后面加上引号:
document.getElementById(test)
becomes 变成
document.getElementById('test')
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