I am looking for a way to retrieve the style from an element that has a style set upon it by the style tag.
In jQuery, you can do alert($("#theid").css("width"))
.
-- if you haven't taken a look at jQuery, I highly recommend it; it makes many simple javascript tasks effortless.
for the record, this post is 5 years old. The web has developed, moved on, etc. There are ways to do this with Plain Old Javascript, which is better.
By using .css() in jquery the style tag can be accessed and modified
for example:
var color = $( this ).css( "background-color" );
$( "#result" ).html( "That div is <span style='color:" +
color + ";'>" + color + "</span>." );
You can make function getStyles
that'll take an element and other arguments are properties that's values you want.
const convertRestArgsIntoStylesArr = ([...args]) => {
return args.slice(1);
}
const getStyles = function () {
const args = [...arguments];
const [element] = args;
let stylesProps = [...args][1] instanceof Array ? args[1] : convertRestArgsIntoStylesArr(args);
const styles = window.getComputedStyle(element);
const stylesObj = stylesProps.reduce((acc, v) => {
acc[v] = styles.getPropertyValue(v);
return acc;
}, {});
return stylesObj;
};
Now, you can use this function like this:
const styles = getStyles(document.body, "height", "width");
OR
const styles = getStyles(document.body, ["height", "width"]);
The element.style property lets you know only the CSS properties that were defined as inline in that element (programmatically, or defined in the style attribute of the element), you should get the computed style.
Is not so easy to do it in a cross-browser way, IE has its own way, through the element.currentStyle
property, and the DOM Level 2 standard way, implemented by other browsers is through the document.defaultView.getComputedStyle method.
The two ways have differences, for example, the IE element.currentStyle property expect that you access the CCS property names composed of two or more words in camelCase (e.g. maxHeight
, fontSize
, backgroundColor
, etc), the standard way expects the properties with the words separated with dashes (e.g. max-height
, font-size
, background-color
, etc).
Also, the IE element.currentStyle
will return all the sizes in the unit that they were specified, (e.g. 12pt, 50%, 5em), the standard way will compute the actual size in pixels always.
I made some time ago a cross-browser function that allows you to get the computed styles in a cross-browser way:
function getStyle(el, styleProp) {
var value, defaultView = (el.ownerDocument || document).defaultView;
// W3C standard way:
if (defaultView && defaultView.getComputedStyle) {
// sanitize property name to css notation
// (hypen separated words eg. font-Size)
styleProp = styleProp.replace(/([A-Z])/g, "-$1").toLowerCase();
return defaultView.getComputedStyle(el, null).getPropertyValue(styleProp);
} else if (el.currentStyle) { // IE
// sanitize property name to camelCase
styleProp = styleProp.replace(/\-(\w)/g, function(str, letter) {
return letter.toUpperCase();
});
value = el.currentStyle[styleProp];
// convert other units to pixels on IE
if (/^\d+(em|pt|%|ex)?$/i.test(value)) {
return (function(value) {
var oldLeft = el.style.left, oldRsLeft = el.runtimeStyle.left;
el.runtimeStyle.left = el.currentStyle.left;
el.style.left = value || 0;
value = el.style.pixelLeft + "px";
el.style.left = oldLeft;
el.runtimeStyle.left = oldRsLeft;
return value;
})(value);
}
return value;
}
}
The above function is not perfect for some cases, for example for colors, the standard method will return colors in the rgb(...) notation, on IE they will return them as they were defined.
I'm currently working on an article in the subject, you can follow the changes I make to this function here.
I believe you are now able to use Window.getComputedStyle()
Documentation MDN
var style = window.getComputedStyle(element[, pseudoElt]);
Example to get width of an element:
window.getComputedStyle(document.querySelector('#mainbar')).width