get value from css using document.getElementById().style.height javascript

Question

Please offer insight into this mystery.

I am trying to get the height value from a div box by

var high = document.getElementById("hintdiv").style.height; 
alert(high);

I can get this value just fine if the attribute is contained within the div tag, but it returns a blank value if the attribute is defined in the css section.

This is fine, it shows 100px as a value. The value can be accessed.

<div id="hintdiv" style="height:100px; display: none;">
.
.
var high = document.getElementById("hintdiv").style.height; 
    alert(high); 

This is not fine, it shows an empty alert screen. The value is practically 0.

#hintdiv
{
height:100px
display: none; 
}

<div id="hintdiv">
.
.
var high = document.getElementById("hintdiv").style.height; 
    alert(high); 

But I have no problem accessing/changing the "display:none" attribute whether it is in the tag or in the css section. The div box displays correctly by both attribute definition methods (inside the tag or in the css section).

I also tried to access the value by other variations, but no luck

document.getElementById("hintdiv").style.height.value  ----> undefined
document.getElementById("hintdiv").height ---->undefined
document.getElementById("hintdiv").height.value  ----> error, no execution

Any solution?

TIA.

Answer 1

This is because, when you use document.getElementById("hintdiv").style.height; you are accessing the style attribute of the tag. If the attribute is not there , then you get no values.

Instead you should use currentStyle object in IE and getComputedStyle() function in the rest of web browsers.

Answer 2

You CSS syntax is wrong, it sould be height:100px; rather than height:100px. Note the semicolon.