Modified version of MyFonts.com font loader that allows style linking (use bold and italic without specifying a font-family every time)

myfonts-style-linking.js

/**
 * ────────────────────────────────────────────────────────────────────────────┐
 * Modified MyFonts JavaScript font loader 
 * 
 * The JavaScript font loader that is included with MyFonts font kits forces the
 * use of unique font-family names, and requires you to set font-weight and 
 * font-style to 'normal' globally. Anywhere you are using bold or italic, a 
 * bold or italic font-family will need to be referenced in your CSS. This can 
 * cause a few issues, including having more styles to override, and worse, if
 * the font files don't load, any and all bold/italic text will just look like
 * normal text. 
 * 
 * This modified version allows for style linking. With style linking, the same 
 * font-family is used across multiple @font-face at-rules. Each @font-face 
 * references a unique font file and includes a unique combination of 
 * font-weight and font-style properties. Once that is set up, it allows you to
 * set the font-family once for all body text, for example, and any instances of
 * bold or italic text will be shown using the corresponding font file. There 
 * is no need to set a font-family anywhere the bold or italic font should 
 * appear; 'font-weight: bold' or 'font-style: italic' will do. Style linking is
 * explained well here: http://j.mp/2wRPnpn.
 * 
 * The modifications start at line 194 ('var fonts'). The original script is 
 * included as a first revision for comparison purposes.
 *
 * NOTE: This is based on formerly minified code. 'Prettifying' isn't always 
 * pretty. Some cleanup was done for readability.
 * ────────────────────────────────────────────────────────────────────────────┘
 */


var protocol = document.location.protocol;
"https:" != protocol && (protocol = "http:");
var count = document.createElement("script");
count.type = "text/javascript";
count.async = !0;
count.src = protocol + "//hello.myfonts.net/count/YOUR_FONT_KIT_ID";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(count, s);
var svgEnabled = 0
var woff2Enabled = 1;
var browserName,
	browserVersion,
	webfontType;

if ("undefined" == typeof woffEnabled) {
	var woffEnabled = !0;
}

if ("undefined" != typeof customPath) {
	var path = customPath;
} else {
	var scripts = document.getElementsByTagName("SCRIPT")
		, script = scripts[scripts.length - 1].src;
	script.match("://") || "/" == script.charAt(0) || (script = "./" + script);
	path = script.replace(/\\/g, "/").replace(/\/[^\/]*\/?$/, "")
}

var wfpath = path + "/fonts/";
var browsers = [{
		regex: "MSIE (\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 9,
			type: "woff"
		}, {
			version: 5,
			type: "eot"
		}]
	}, {
		regex: "Trident/(\\d+\\.\\d+); (.+)?rv:(\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$3)",
		type: [{
			version: 11,
			type: "woff"
		}]
	}, {
		regex: "Firefox[/s](\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 3.6,
			type: "woff"
		}, {
			version: 3.5,
			type: "ttf"
		}]
	}, {
		regex: "Edge/(\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 12,
			type: "woff"
		}]
	}, {
		regex: "Chrome/(\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 36,
			type: "woff2"
		}, {
			version: 6,
			type: "woff"
		}, {
			version: 4,
			type: "ttf"
		}]
	}, {
		regex: "Mozilla.*Android (\\d+\\.\\d+).*AppleWebKit.*Safari",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 4.1,
			type: "woff"
		}, {
			version: 3.1,
			type: "svg#wf"
		}, {
			version: 2.2,
			type: "ttf"
		}]
	}, {
		regex: "Mozilla.*(iPhone|iPad).* OS (\\d+)_(\\d+).* AppleWebKit.*Safari",
		versionRegex: "new Number(RegExp.$2) + (new Number(RegExp.$3) / 10)",
		unhinted: !0,
		type: [{
			version: 5,
			type: "woff"
		}, {
			version: 4.2,
			type: "ttf"
		}, {
			version: 1,
			type: "svg#wf"
		}]
	}, {
		regex: "Mozilla.*(iPhone|iPad|BlackBerry).*AppleWebKit.*Safari",
		versionRegex: "1.0",
		type: [{
			version: 1,
			type: "svg#wf"
		}]
	}, {
		regex: "Version/(\\d+\\.\\d+)(\\.\\d+)? Safari/(\\d+\\.\\d+)",
		versionRegex: "new Number(RegExp.$1)",
		type: [{
			version: 5.1,
			type: "woff"
		}, {
			version: 3.1,
			type: "ttf"
		}]
	}, {
		regex: "Opera/(\\d+\\.\\d+)(.+)Version/(\\d+\\.\\d+)(\\.\\d+)?",
		versionRegex: "new Number(RegExp.$3)",
		type: [{
			version: 24,
			type: "woff2"
		}, {
			version: 11.1,
			type: "woff"
		}, {
			version: 10.1,
			type: "ttf"
		}]
	}];

var browLen = browsers.length;
var suffix = "";
var i = 0;

a: for (; i < browLen; i++) {
	var regex = new RegExp(browsers[i].regex);
	if (regex.test(navigator.userAgent)) {
		browserVersion = eval(browsers[i].versionRegex);
		var typeLen = browsers[i].type.length;
		for (j = 0; j < typeLen; j++) {
			if (browserVersion >= browsers[i].type[j].version && (1 == browsers[i].unhinted && (suffix = "_unhinted"),
				webfontType = browsers[i].type[j].type,
				"woff" != webfontType || woffEnabled) && ("woff2" != webfontType || woff2Enabled) && ("svg#wf" != webfontType || svgEnabled)) {
				break a;
			}
		}
	} else {
		webfontType = "woff"
	}
}

/(Macintosh|Android)/.test(navigator.userAgent) && "svg#wf" != webfontType && (suffix = "_unhinted");
var head = document.getElementsByTagName("head")[0],
	stylesheet = document.createElement("style");

stylesheet.setAttribute("type", "text/css");
head.appendChild(stylesheet);

for (var fonts = [{
	// Body font, bold -- SomeFont - Heavy
	fontFamily: "SomeFont", // Same font-family used for all 3 body fonts...
	url: wfpath + "YOUR_FONT_KIT_ID_0" + suffix + "_0." + webfontType,
	fontWeight: "bold",     // ...but source file, font-weight and 
	fontStyle: "normal"     // font-style vary. This sets up style linking.
}, {
	// Body font, italic -- SomeFont - Oblique
	fontFamily: "SomeFont", // See above
	url: wfpath + "YOUR_FONT_KIT_ID_1" + suffix + "_0." + webfontType,
	fontWeight: "normal",
	fontStyle: "italic"
}, {
	// Body font, normal -- SomeFont - Roman
	fontFamily: "SomeFont", // See above
	url: wfpath + "YOUR_FONT_KIT_ID_2" + suffix + "_0." + webfontType,
	fontWeight: "normal",
	fontStyle: "normal"
}, {
	// Heading font -- SomeFont - Light
	fontFamily: "SomeFont-Light", // The heading font has its own font-family,
	                              // though it could be given another weight
	                              // instead (e.g. fontWeight: "300"), in which
	                              // case the font-family could be the same as
	                              // the one used for the body font.
	url: wfpath + "YOUR_FONT_KIT_ID_3" + suffix + "_0." + webfontType,
	fontWeight: "normal",
	fontStyle: "normal"
}], len = fonts.length, css = "", i = 0; i < len; i++) {
	var format = "svg#wf" == webfontType ? 'format("svg")' : "ttf" == webfontType ? 'format("truetype")' : "eot" == webfontType ? "" : 'format("' + webfontType + '")',
		 css = css + ("@font-face{font-family: " + fonts[i].fontFamily + ";src:url(" + fonts[i].url + ")" + format + ";");
	
	// fonts[i].fontWeight is defined, unlike in the original
	fonts[i].fontWeight && (css += "font-weight: " + fonts[i].fontWeight + ";");
	// fonts[i].fontStyle is defined, unlike in the original
	fonts[i].fontStyle && (css += "font-style: " + fonts[i].fontStyle + ";");
	css += "}"
}
stylesheet.styleSheet ? stylesheet.styleSheet.cssText = css : stylesheet.innerHTML = css;