How Can I Access CSS-Generated Content Using JavaScript?

Accessing CSS Generated Content with JavaScript

Within CSS, counters and content properties can be used to generate dynamic content, such as numbering headers and figures. However, accessing this generated content in JavaScript presents challenges, as the live values may not be readily accessible through standard methods.

Accessing Counter Values

One approach is to utilize the DOM Level 2 Style Counter interface. However, this method has limitations, as evidenced by the error encountered when attempting to access the counter value using getCounterValue().

Accessing Generated Content

Another possibility is to identify the pseudo-element (:after in this case) and extract its node value. However, this approach may also be unreliable due to the lack of a standard mechanism for accessing pseudo-element content via the DOM.

Workarounds

As a workaround, a script-based solution can be implemented that simulates the browser's counting mechanism. This involves traversing the DOM to count the number of elements that trigger the counter and inserting appropriate values.

window.onload = function () {
    var counters = document.querySelectorAll('.counter');
    var indices = [];
    for (var i = 0; i < counters.length; i++) {
        var counter = counters[i];
        var level = parseInt(counter.getAttribute('level'));
        while (indices.length <= level) indices.push(0);
        indices[level]++;
        indices = indices.slice(level + 1);
        var text = document.createTextNode('Figure ' + indices.join('.'));
        counter.parentNode.insertBefore(text, counter.nextSibling);

        if (counter.id !== '') {
            for (var j = 0; j < document.links.length; j++) {
                var link = document.links[j];
                if (
                    link.hostname === location.hostname &&
                    link.pathname === location.pathname &&
                    link.search === location.search &&
                    link.hash === '#' + counter.id
                ) {
                    var text = document.createTextNode('(' + indices.join('.') + ')');
                    link.parentNode.insertBefore(text, link.nextSibling);
                }
            }
        }
    }
};

This approach mimics the browser's behavior by explicitly updating the counter values and generating appropriate labels. It provides a more portable and reliable solution than relying on live counter values, especially in environments where such information is inaccessible via standard APIs.

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