It's easy to set inline CSS values with javascript. If I want to change the width and I have html like this:
<div style="width: 10px"></div>
All I need to do is:
document.getElementById('id').style.width = value;
It will change the inline stylesheet values. Normally this isn't a problem, because the inline style overrides the stylesheet. Example:
<style>
#tId {
width: 50%;
}
</style>
<div id="tId"></div>
Using this Javascript:
document.getElementById('tId').style.width = "30%";
I get the following:
<style>
#tId {
width: 50%;
}
</style>
<div id="tId" style="width: 30%";></div>
This is a problem, because not only do I not want to change inline values, If I look for the width before I set it, when I have:
<div id="tId"></div>
The value returned is Null, so if I have Javascript that needs to know the width of something to do some logic (I increase the width by 1%, not to a specific value), getting back Null when I expect the string "50%" doesn't really work.
So my question: I have values in a CSS style that are not located inline, how can I get these values? How can I modify the style instead of the inline values, given an id?
This question is related to
javascript
html
css
ajax
dom
Gathering the code in the answers, I wrote this function that seems running well on my FF 25.
function CCSStylesheetRuleStyle(stylesheet, selectorText, style, value){
/* returns the value of the element style of the rule in the stylesheet
* If no value is given, reads the value
* If value is given, the value is changed and returned
* If '' (empty string) is given, erases the value.
* The browser will apply the default one
*
* string stylesheet: part of the .css name to be recognized, e.g. 'default'
* string selectorText: css selector, e.g. '#myId', '.myClass', 'thead td'
* string style: camelCase element style, e.g. 'fontSize'
* string value optionnal : the new value
*/
var CCSstyle = undefined, rules;
for(var m in document.styleSheets){
if(document.styleSheets[m].href.indexOf(stylesheet) != -1){
rules = document.styleSheets[m][document.all ? 'rules' : 'cssRules'];
for(var n in rules){
if(rules[n].selectorText == selectorText){
CCSstyle = rules[n].style;
break;
}
}
break;
}
}
if(value == undefined)
return CCSstyle[style]
else
return CCSstyle[style] = value
}
This is a way to put values in the css that will be used in JS even if not understood by the browser. e.g. maxHeight for a tbody in a scrolled table.
Call :
CCSStylesheetRuleStyle('default', "#mydiv", "height");
CCSStylesheetRuleStyle('default', "#mydiv", "color", "#EEE");
Perhaps try this:
function CCSStylesheetRuleStyle(stylesheet, selectorText, style, value){
var CCSstyle = undefined, rules;
for(var m in document.styleSheets){
if(document.styleSheets[m].href.indexOf(stylesheet) != -1){
rules = document.styleSheets[m][document.all ? 'rules' : 'cssRules'];
for(var n in rules){
if(rules[n].selectorText == selectorText){
CCSstyle = rules[n].style;
break;
}
}
break;
}
}
if(value == undefined)
return CCSstyle[style]
else
return CCSstyle[style] = value
}
I don't have rep enough to comment so I'll format an answer, yet it is only a demonstration of the issue in question.
It seems, when element styles are defined in stylesheets they are not visible to getElementById("someElement").style
This code illustrates the issue... Code from below on jsFiddle.
In Test 2, on the first call, the items left value is undefined, and so, what should be a simple toggle gets messed up. For my use I will define my important style values inline, but it does seem to partially defeat the purpose of the stylesheet.
Here's the page code...
<html>
<head>
<style type="text/css">
#test2a{
position: absolute;
left: 0px;
width: 50px;
height: 50px;
background-color: green;
border: 4px solid black;
}
#test2b{
position: absolute;
left: 55px;
width: 50px;
height: 50px;
background-color: yellow;
margin: 4px;
}
</style>
</head>
<body>
<!-- test1 -->
Swap left positions function with styles defined inline.
<a href="javascript:test1();">Test 1</a><br>
<div class="container">
<div id="test1a" style="position: absolute;left: 0px;width: 50px; height: 50px;background-color: green;border: 4px solid black;"></div>
<div id="test1b" style="position: absolute;left: 55px;width: 50px; height: 50px;background-color: yellow;margin: 4px;"></div>
</div>
<script type="text/javascript">
function test1(){
var a = document.getElementById("test1a");
var b = document.getElementById("test1b");
alert(a.style.left + " - " + b.style.left);
a.style.left = (a.style.left == "0px")? "55px" : "0px";
b.style.left = (b.style.left == "0px")? "55px" : "0px";
}
</script>
<!-- end test 1 -->
<!-- test2 -->
<div id="moveDownThePage" style="position: relative;top: 70px;">
Identical function with styles defined in stylesheet.
<a href="javascript:test2();">Test 2</a><br>
<div class="container">
<div id="test2a"></div>
<div id="test2b"></div>
</div>
</div>
<script type="text/javascript">
function test2(){
var a = document.getElementById("test2a");
var b = document.getElementById("test2b");
alert(a.style.left + " - " + b.style.left);
a.style.left = (a.style.left == "0px")? "55px" : "0px";
b.style.left = (b.style.left == "0px")? "55px" : "0px";
}
</script>
<!-- end test 2 -->
</body>
</html>
I hope this helps to illuminate the issue.
Skip
I've never seen any practical use of this, but you should probably consider DOM stylesheets. However, I honestly think that's overkill.
If you simply want to get the width and height of an element, irrespective of where the dimensions are being applied from, just use element.offsetWidth and element.offsetHeight.
You can get the "computed" styles of any element.
IE uses something called "currentStyle", Firefox (and I assume other "standard compliant" browsers) uses "defaultView.getComputedStyle".
You'll need to write a cross browser function to do this, or use a good Javascript framework like prototype or jQuery (search for "getStyle" in the prototype javascript file, and "curCss" in the jquery javascript file).
That said if you need the height or width you should probably use element.offsetHeight and element.offsetWidth.
The value returned is Null, so if I have Javascript that needs to know the width of something to do some logic (I increase the width by 1%, not to a specific value)
Mind, if you add an inline style to the element in question, it can act as the "default" value and will be readable by Javascript on page load, since it is the element's inline style property:
<div style="width:50%">....</div>
I don't know why the other solutions go through the whole list of stylesheets for the document. Doing so creates a new entry in each stylesheet, which is inefficient. Instead, we can simply append a new stylesheet and simply add our desired CSS rules there.
style=document.createElement('style');
document.head.appendChild(style);
stylesheet=style.sheet;
function css(selector,property,value)
{
try{ stylesheet.insertRule(selector+' {'+property+':'+value+'}',stylesheet.cssRules.length); }
catch(err){}
}
Note that we can override even inline styles set directly on elements by adding " !important" to the value of the property, unless there already exist more specific "!important" style declarations for that property.
Please! Just ask w3 (http://www.quirksmode.org/dom/w3c_css.html)! Or actually, it took me five hours... but here it is!
function css(selector, property, value) {
for (var i=0; i<document.styleSheets.length;i++) {//Loop through all styles
//Try add rule
try { document.styleSheets[i].insertRule(selector+ ' {'+property+':'+value+'}', document.styleSheets[i].cssRules.length);
} catch(err) {try { document.styleSheets[i].addRule(selector, property+':'+value);} catch(err) {}}//IE
}
}
The function is really easy to use.. example:
<div id="box" class="boxes" onclick="css('#box', 'color', 'red')">Click Me!</div>
Or:
<div class="boxes" onmouseover="css('.boxes', 'color', 'green')">Mouseover Me!</div>
Or:
<div class="boxes" onclick="css('body', 'border', '1px solid #3cc')">Click Me!</div>
Oh..
(function (scope) {
// Create a new stylesheet in the bottom
// of <head>, where the css rules will go
var style = document.createElement('style');
document.head.appendChild(style);
var stylesheet = style.sheet;
scope.css = function (selector, property, value) {
// Append the rule (Major browsers)
try { stylesheet.insertRule(selector+' {'+property+':'+value+'}', stylesheet.cssRules.length);
} catch(err) {try { stylesheet.addRule(selector, property+':'+value); // (pre IE9)
} catch(err) {console.log("Couldn't add style");}} // (alien browsers)
}
})(window);
This simple 32 lines gist lets you identify a given stylesheet and change its styles very easily:
var styleSheet = StyleChanger("my_custom_identifier");
styleSheet.change("darkolivegreen", "blue");
Source: Stackoverflow.com