Reading class names in a stylesheet

Question

I have an HTML document that uses multiple style tags. One of those styles has the following content

<style id='pstyle'>
.p0010, .p0016, .p0022, .p0028, .p0032, 
.p0034, .p0038, .p0042, .p0044, .p0046, 
.p0048, .p0050, .p0052, .p0054, .p0056, 
{
 max-width:100%; 
 background-size:100%; 
 background-image: url('sprites.png');
}
</style>

document.styleSheets allows me to access the full set of stylesheets used by the document. From there - once I have grabbed the right stylesheet - I can use the cssRules array attribute to access the selectorText attribute of each contained style. However, I have been unable to figure out how to find the "right" style sheet. Whilst I can give the stylesheet an id this does not turn up as an attribute of the document.styleSheets[n] object.

I do a great deal of DOM manipulation but it is mostly with the visual elements in the document. I'd be much obliged to anyone who can tell me how I go about identifying the "right" stylesheet

---

A plain English version of the task

a. Find the style element - bearing in mind that there will be others - with the id pstyle b. Read the class names defined therein and do whatever

Answer 1

I'm not sure to understand if you want to get the stylesheet associated with the <style> element, or if you want to retrieve the element from the stylesheet.

So here you'll get both :

// from the element
console.log(pstyle.sheet === document.styleSheets[2]);
// from the stylesheet
console.log(document.styleSheets[2].ownerNode === pstyle);

<style id='pstyle'>
</style>

_{note that in the snippet it's [2] because stacksnippet does inject stylesheets}

And now to get the cssRules and selectorText, you just have to read it from the selected styleSheet:

var pstyle = document.getElementById('pstyle');

// from the element
console.log(pstyle.sheet.cssRules[0].selectorText);

// from the stylesheets
for(var sheet of document.styleSheets){
  if(sheet.ownerNode === pstyle){
    console.log(sheet.cssRules[0].selectorText);
    }
  }

<style id='pstyle'>
.p0010, .p0016, .p0022, .p0028, .p0032, 
.p0034, .p0038, .p0042, .p0044, .p0046, 
.p0048, .p0050, .p0052, .p0054, .p0056 
{
 max-width:100%; 
 background-size:100%; 
 background-image: url('sprites.png');
}
</style>