Iphone like shortening function to short Text

gistfile1.js

var longText = "Super Duper Long Description from the manual for the dashboard";
var shortText = "Main Screen";

var shortTxt = function(txt,max,fill) {

	var sTxt = txt, 
	max = max || 12, 
	fill = fill || '...';
	
	if(txt.length>=max){
		var offset = Math.floor(((max-fill.length) / 2));
		var offsetLeft = (offset*2)<(max+fill.length) ? (offset+1) : offset;
		
		sTxt =  txt.substr(0,offsetLeft) + fill + txt.substr((0-offset));
	}
	
	return sTxt;
}

console.log(shortTxt(longText)); // Super...oard
console.log(shortTxt(shortText)); // Main Screen