function randomNum(from, to) {
	return from + Math.floor( Math.random() * (to - from + 1) );
}
function randomChar(length){
	var library = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
	var res = '';
	for(var i=0; i<length; i++){
		res = [res, library[randomNum(0,9)]].join('');
	}
	return res;
}

// randomChar(140)