aliascss/lib/compilers/url.js

AliasCSS is a CSS post processor.

export default function url(data) {
    // bg-url3-path-to-folder-png
    // bg-url3_path_to-the_folder_name_png
    let holder = '';
    data.split(/__/).forEach((each) => {
        each = each.replace(/^[-]?url/, '');
        if (each.match(/^--[a-zA-Z]/)) {
            holder += `url(var(${each})),`;
            return;
        }
        let dir = '';
        if (each.match(/^[-]?[\d][-_]/)) {
            const ndir = /^([0-9])[-_]/.exec(each);
            if (ndir)
                for (let i = 0; i < parseInt(ndir[1], 10); i++) {
                    dir += '../';
                }
            each = each.replace(/^[\d]/, '');
        }
        if (!/^[-_]/.test(each)) {
            each = '-' + each;
        }
        const divider = each.slice(0, 1);
        each = each
            .replace(/^[-_]/, '')
            .replace(new RegExp(divider, 'g'), '/')
            .replace(/[\/]([a-z0-9]+)$/, '.$1');
        holder += "url('" + dir + each + "'),";
    });
    return holder.replace(/[,]$/, '').trim();
    // note restriction not use folder with name that uses ../../also need to figure out for
    // bg-url_3_path_to_folder-name_name_png--3_
}