JavaScript调试问题

JavaScript调试问题

获取element.style.width为空

请参考Width of a DIV is nothing according to Javascript, why?

new problem. document.getElementById().width returning unassigned. why

如：

<style>
div#foot_wrapper{
width:650px;
height:20px;
position:absolute;
bottom:10px;
background-color:#000000;
}
</style>
<script>

function align(div){
alert(div.style.width); // ---------------- box pops up blank?
div.style.left = (window.innerWidth/2) - (div.style.width/2);
}
</script>

alert(div.style.width)

弹出为空

主要原因为：

The style property only reflects the styles that were set inline on an element (using the style attribute on the element).

可以使用

div.offsetWidth

来代替

return vs no return

参考：Javascript onclick return functionality

如下：

<input type="checkbox" onclick="doAlert()" />

与

<input type="checkbox" onclick="return doAlert();" />

与

<a href='#' onclick='someFunc(3.1415926); return false;'>Click here !</a>

类似

The return value of an event handler determines whether or not the default browser behaviour should take place as well.

event handler的返回值用来确定浏览器的默认行为是否发生