This gist adds two methods HexToRGB() and RGBToHex() to String and Array prototypes in JavaScript.

Conversion: RGB to Hex and vice versa

String.prototype.hexToRGB = function(){
    if (this[0] === "#" && this.length === 7){ 
   		return String.prototype.hexToRGB.call(this.slice(1)); 
        }
    if (!/^[a-fA-F\d]{6}$/.test(this) || this.length > 6){
		throw new SyntaxError("String is not a valid hex number");
	}
	var str = "(";
	for (var i=0; i<=this.length-2; i+=2){
		str+=(parseInt(this.substr(i,2),16));
		if( i !== this.length-2) {
			str+=",";
		}
	}
	return str+")";
}

String.prototype.rgbToHex = function (){ 
	var temp = this;
	if(this[0] === "(" && this[this.length-1] === ")") {
		temp = this.slice(1,this.length-1);
	}
	temp = temp.split(",");
	if (temp.length !== 3){
		throw "String is not RGB";
	}
	return temp.rgbToHex();
}

Array.prototype.rgbToHex = function (){ 
	var str = "";
	for (var i=0; i<this.length; i++) { 
		str+=((parseInt(this[i],10) <= 255 ? parseInt(this[i],10) : eval('throw new SyntaxError("String ("+parseInt(this[i],10)+") is not a valid hex number")')).toString(16));
	} 
	return str; 
}

/* Examples */
/* "#ffffff".HexToRGB() gives "(255,255,255)" */
/* "ffffef".HexToRGB() gives "(255,255,239)" */
/* "(255,255,239)".RGBToHex() gives "ffffef" */
/* "255,255,239".RGBToHex() gives "ffffef" */
/* [255,255,239].RGBToHex() gives "ffffef" */