Javascript函数无法使用onmouseover属性

Question

I want to change css property when mouse is over/out on images. Unfortunately, it didn't seem to work, so I tested simple javascript with onmouseover attribute:

<script type="text/javascript">
    function show_alert() { document.alert("Alert"); }
</script>

and

<div class="test" onmouseover="show_alert()">
  ....
</div>

but when I moved mouse over this div block, nothing happened and kinda hard to debug what was going inside. How can I resolve this problem ?

Answer 1

The alert doesn't work because you're using document.alert , which doesn't exist. You'll be wanting window.alert , or just alert

Check out this JSFiddle

Answer 2

The alert method is a method of the window object, not the document object. Using document.alert returns undefined .

<script type="text/javascript">
  function show_alert() { window.alert("Alert"); }
</script>

Answer 3

I want to change css property when mouse is over/out on images

why do you need javascript for this? A simple CSS Style does the trick:

img:hover { border: 2px solid red; }

By the way

document as no property called alert . It's window.alert() ! or simply alert('hello');