Is there a reason why the alert says undefined is loaded?
function test(object) {
var id = object.id;
alert(id + " is loaded");
}<body id="test" onload="test(this);">
<h1>Hello World!</h1>
</body>Is there a reason why the alert says undefined is loaded?
function test(object) {
var id = object.id;
alert(id + " is loaded");
}<body id="test" onload="test(this);">
<h1>Hello World!</h1>
</body>
Share Improve this question edited Aug 26, 2018 at 6:15 Ramesh 2,4132 gold badges24 silver badges44 bronze badges asked Aug 26, 2018 at 4:37 zerodramazerodrama 511 silver badge6 bronze badges 3- Have you tried put the script before /body ? – A. Meshu Commented Aug 26, 2018 at 4:42
- Interesting will try – zerodrama Commented Aug 26, 2018 at 4:43
- This might work with img onerror stackoverflow./questions/4057236/… – zerodrama Commented Aug 26, 2018 at 5:25
3 Answers
Reset to default 2In JavaScript, the this on the onload event on body refers to window instead of body. However, the onload on image elements (and iframe) refers to the element itself. To get around this, I would change your code to:
test(document.body)
Proof of how onload works JavaScript:
<!DOCTYPE html>
<html>
<head>
<script>
function test(object) {
console.log("" + object);
}
</script>
</head>
<body id="test" onload="test(this)">
<img src="https://www.google/assets/static/images/logo_googledotorg-171e7482e5523603fc0eed236dd772d8.svg" onload="test(this)" />
<h1>Hello World!</h1>
</body>
</html>"this" in your onload function will refer to the window object, not to the body element itself. In your onload function, you'll need to do a getElementById('test') to get the body's id.
I prefer window.onload than document.body.onload because it is less obtrusive. But, both however are the same.
function test(object) {
var id = object.id;
alert(id + " is loaded");
}
window.onload = function(){ test(document.body); }<body id="test">
<h1>Hello World!</h1>
</body>I moved the onload event to the JavaScript.