js_random.js

function _r(maxlength){
	maxlength = (maxlength && typeof maxlength === 'number') ? maxlength : 20;
	var result = [];
	var template = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	template += "abcdefghijklmnopqrstuvwxyz";
	template += "0123456789";
	template += "`~!@#$%^&*()_+№;:?-=";
	
	while(result.length < maxlength){
		var c = template.charAt(Math.floor(Math.random() * template.length));
		if(result.indexOf(c) < 0){
			result.push(c);
		}
	}
	return result.join('');
}

console.time("random");
for(var i = 0; i < 10000; i++){
	console.log(_r());
}
console.timeEnd("random");