function to parse LESS variables to Javascript

getLessVars.js

/**
 * getLessVars parses your LESS variables to Javascript (provided you make a dummy node in LESS)
 * @param {String} id The CSS-id your variables are listed under.
 * @param {Boolean} [parseNumbers=true] Try to parse units as numbers.
 * @return {Object} A value object containing your LESS variables.
 * @example
 * LESS:
 * 	@myLessVariable: 123px;
 * 	#dummyLessId { width: @myLessVariable; }
 * Javascript:
 * 	getLessVars('dummyLessId');
 * returns:
 * 	{myLessVariable:123}
 */
function getLessVars(id,parseNumbers) {
	var bNumbers = parseNumbers===undefined?true:parseNumbers
		,oLess = {}
		,rgId = /\#[\w-]+/
		,rgKey = /\.([\w-]+)/
		,rgUnit = /[a-z]+$/
		,aUnits = 'em,ex,ch,rem,vw,vh,vmin,cm,mm,in,pt,pc,px,deg,grad,rad,turn,s,ms,Hz,kHz,dpi,dpcm,dppx'.split(',')
		,rgValue = /:\s?(.*)\s?;\s?\}/
		,rgStr = /^'([^']+)'$/
		,sId = '#'+id
		,oStyles = document.styleSheets;
	for (var i=0,l=oStyles.length;i<l;i++) {
		var oRules;
		try{ oRules = oStyles[i].cssRules; }
		catch (e) { continue; }
		if (oRules) {
			for (var j=0,k=oRules.length;j<k;j++) {
				try { var sRule = oRules[j].cssText; }
				catch (e) { continue; }
				var aMatchId = sRule.match(rgId);
				if (aMatchId&&aMatchId[0]==sId) {
					var aKey = sRule.match(rgKey)
						,aVal = sRule.match(rgValue);
					if (aKey&&aVal) {
						var sKey = aKey[1]
							,oVal = aVal[1]
							,aUnit
							,aStr;
						if (bNumbers&&(aUnit=oVal.match(rgUnit))&&aUnits.indexOf(aUnit[0])!==-1) {
							oVal = parseFloat(oVal);
						} else if (aStr=oVal.match(rgStr)) {
							oVal = aStr[1];
						}
						oLess[sKey] = oVal;
					}
				}
			}
		}
	}
	return oLess;
}

package.json

{
  "name": "getLessVars",
  "version": "0.1.0"
}

Examples:
http://jsfiddle.net/Sjeiti/VHQ8x/
http://jsfiddle.net/Sjeiti/WdyGy/

This doesn't allow for hyphenated variables names. Modifying these two lines seems to work:

    ,rgId = /\#[\w-]+/
    ,rgKey = /\.([\w-]+)/

Also this function fails in Firefix when including external stylesheets (such as Google Web Fonts) because of a security exception. To step around that change:

var oRules = oStyles[i].cssRules;

to:

try{ var oRules = oStyles[i].cssRules; }
catch (e) { continue; }

This thing is great! Thank you!

nathanpbell's comment is true for IE11 too.

There's an error in IE10 when the LESS variables include a keyframe rule—the cssText attribute isn't available (see http://jsbin.com/jituquqewe/edit?html,output for an example).

Same workound approach as above: change

var sRule = oRules[j].cssText,
  aMatchId = sRule.match(rgId);

to

try {
  var sRule = oRules[j].cssText;
}
catch (e) { continue; }
var aMatchId = sRule.match(rgId);