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why doesn't the onload event binds the `this` variable as expected?

开发者 https://www.devze.com 2023-03-10 08:43 出处：网络

does anyone knows why doesn\'t the onload event binds the this variable as expected? Like in this test script, onkeydown gi开发者_开发知识库ves us true (this is working fine) but onload gives us fals

相关专题：javascript web-applications web-services

does anyone knows why doesn't the onload event binds the this variable as expected?

Like in this test script, onkeydown gi开发者_开发知识库ves us true (this is working fine) but onload gives us false (this now points to window.. wth?):

<!DOCTYPE html>
<html><head>
<script>
function f(t){
alert(t===document.body);
}
</script>
</head><body onkeydown="f(this);" onload="f(this);">

</body></html>

See the documentation:

HTMLBodyElement.onload

Exposes the window.onload event handler to call when the window gains focus.

Note that this handler is triggered when the event reaches the window, not the body element. Use addEventListener() to attach an event listener to the body element.

The important part is this handler is triggered when the event reaches the window. The handler is executed in the context of the window and not the body.

FWIW, alert(window.onload === document.body.onload); will yield true.