Javascript Font Loader for Fonts.com that allows multiple weights-per-family

fontscom.loader.js

/*
 * fonts.com implement one different font-family name per weight or style of
 * the same font. This means you need to explicitly declare in your elements
 * that use a font-weight different to `normal` the new font-family
 * corresponding to that weight.
 *
 * See http://stackoverflow.com/questions/5824925/is-there-any-way-to-fix-fonts-com-font-face-declarations
*/

var FontsComLoader = (function() {

    var _get = function(url, callback) {
        var xdomain = 'XDomainRequest' in window && window.XDomainRequest !== null;
        var xhr = xdomain ? new XDomainRequest() : new XMLHttpRequest();

        if (xdomain) {
            xhr.onload = function(data) {
                callback.call(xhr, xhr.responseText);
            };
        }

        xhr.onreadystatechange = function() {
            if (xhr.readyState == 4 && xhr.status == 200) {
                callback.call(xhr, xhr.responseText);
            }
        };

        xhr.open("GET", url, true);
        xhr.send();
    };


    var methods = {
        init: function(name, url, variants) {
            this.name = name;
            this.url = url;
            this.variants = variants;

            this.protocol = window.location.protocol + '//';
            this.fontscomURL = this.protocol + 'fast.fonts.net';
        },

        load: function(name, url, variants) {
            if (!variants || !name || !url) return;

            var ins =  new methods.init(name, url, variants);
            _get(ins.url, function(stylesheet) {
                ins.addStyleTag();
                ins.CSSString = stylesheet;
                ins.appendCSS(ins.parseCSS());
            });
            return ins;
        },

        parseCSS: function(css) {
            css = css || this.CSSString;

            var weight, style, regx;
            css = css.replace(/url\("\//g, 'url("' + this.fontscomURL +'/');
            css = css.replace(/url\('\//g, 'url(\'' + this.fontscomURL + '/');
            css = css.replace(/url\(\//g, 'url(' + this.fontscomURL + '/');

            for (var matchExp in this.variants) {
                regx = new RegExp('(font-family:(.*)' + matchExp + '(.*)";)', 'g');
                weight = typeof this.variants[matchExp] === 'string' ? this.variants[matchExp] :
                       this.variants[matchExp].weight;

                style = this.variants[matchExp].style || 'normal';
                css = css.replace(regx, '$1 font-weight: ' + weight + ';' + 'font-style:' + style + ';');
            }

            css = css.replace(/font-family:(.*)";/g, 'font-family: "' + this.name + '";');

            return css;
        },

        addStyleTag: function() {
            this.scriptTag = document.createElement('style');
            document.head.appendChild(this.scriptTag);
            // this.disable();
            return this;
        },

        appendCSS: function(css) {
            css = css || this.CSSString;
            this.scriptTag.innerHTML = css;
            // this.enable();
            return this;
        },

        disable: function() {
            this.scriptTag.disabled = true;
            return this;
        },

        enable: function() {
            this.scriptTag.disabled = false;
            return this;
        }
    };

    methods.init.prototype = methods;

    return methods;

})();

usage.css

.helvetica-regular,
.helvetica-bold {
    font-family: 'HelveticaNeueFontsCom', 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.helvetica-regular {
    font-weight: 400;
}

.helvetica-bold {
    font-weight: 700;
}

usage.js

/* Keys in object should match font-family names provided by fonts.com, 
 * they will be replaced by 'HelveticaNeueFontsCom' in this case. */


FontsComLoader.load('HelveticaNeueFontsCom', 'https://fast.fonts.net/cssapi/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX.css', {
    'W02-55Roma': '400',
    'W02-75Bold': '700'
});



/*
// It's also posible to specify font-style properties.

FontsComLoader.load('HelveticaNeueFontsCom', 'https://fast.fonts.net/cssapi/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX.css', {
    'W02-55Roma': {
        weight: '400',
        style: 'normal'
    },
    'W02-75Bold': {
        weight: '700',
        style: 'normal'
    }
});
*/