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Changing external style sheets using the DOM

Most of us are familiar with manipulating an element's inline style by accessing its "style" object. There are times however, that you may find it necessary to escalate the issue, and talk directly with the boss upstairs that's the external style sheet on the page. Modifying an external style sheet (style or link tag) is extremely powerful, yet should be noted is less efficient and straightforward than going the route of dynamic inline styles. With that declaration, lets begin!

Key to the gate: the styleSheet object

The styleSheet object of the document contains all the external style sheets on the page, either defined using the <style> or <link rel="stylesheet"> tag: This is how we access external stylesheets in the DOM. For example:

document.styleSheets[0] //access the first external style sheet on the page
document.styleSheets.length //returns the total # of external style sheets

Referencing a particular external style sheet on the page

Now, you may be wondering, "So how do I pick out and reference a specific stylesheet out of numerous on the page? Since the stylesheet[] array only supports reference by position, we can use a for loop and scoop out the one we want. One way is to assign a title attribute to the style sheet of interest (inside its <style> tag) for the purpose of identifying it:

for (i=0; i<document.styleSheets.length; i++){
if (document.styleSheets[i].title=="Blue style") //if style sheet is titled "Blue style"
mycss=document.styleSheets[i] //mycss now contains the style sheet we're looking for

Here I give the style sheet I wish to access on the page a title attribute of "Blue style", so our script can easily pick it out from a lineup.

It's time to look at the styleSheet object in detail now.

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