A bit of code to check if a certain css rule is being use by the site

css-rule-checker.ts

rules = [];
website = "https://www.yoursite.com/";
Array.from(document.styleSheets)
    .filter(x => (x.href || "").startsWith(website))
    .forEach(sheet => {
        Array.from(sheet.rules)
            .filter(x => x.conditionText === undefined)
            .filter(x => x.selectorText !== undefined)
            .filter(x => !x.selectorText.includes(":"))
            .filter(x => ($$(x.selectorText) || []).length == 0)
            .forEach(x => {
                let rulePath = x.selectorText.split(" ").filter(x => x.length);
                let rule = "";
                for(let i = 0; i < rulePath.length; ++i){
                    if(i < rulePath.length){ 
                        rule += " " + rulePath[i];
                        rule = rule.trim();
                     }

                    if(rules.indexOf(rule) !== -1){
                        // Already listed.
                        return;
                    }
                }

                rules.push(rule);
            });
    });

// Remove the rules that are too
rules = rules.sort();
rules = rules.filter(x => {
    let parts = x.split(" ");
    let rule = "";
    for(let i = 0; i < (parts.length - 1); ++i){
        rule = (rule + " " + parts[i]).trim();
        if(rules.indexOf(rule) !== -1){
            // Already listed.
            return false;
        }
    }
    return true
})
    
// Check if a rule is used on another page
usedOnSomePage = [];
rules_1.filter(a => rules_2.indexOf(a) === -1).forEach(a => usedOnSomePage.push(a));
rules_2.filter(a => rules_1.indexOf(a) === -1).forEach(a => usedOnSomePage.push(a));
b = [...rules_1, ...rules_2];
b = b.filter(a => usedOnSomePage.indexOf(a) === -1);
usedOnSomePage = usedOnSomePage.filter(onlyUnique); 
b = b.filter(onlyUnique)