none

leftpad nice!

function leftpad1(str, len, ch) {
	if (!ch&&ch!=0) ch=' ';
	len = len - str.length;
	var pad = ''; var i = -1;
	while (++i < len) {
		pad = ch + pad;
	}
	return pad+str;
}

function leftpad2(str, len, ch) {
	if (!ch&&ch!=0) ch=' ';
	len = len - str.length;
	var pad = Array(len+1).join(ch);
	return pad+str;
}

function leftpad3(str, len, ch) {
	if (!ch&&ch!=0) ch=' ';
	len = len - str.length;
	var pad = ''; while (true) {
		if (len&1) pad += ch;
		if (len>>=1) ch += ch;
		else break;
	}
	return pad+str;
}

var leftpad4 = (str,n,ch) => ((new Array(n)).join(ch||' ') + str).slice(-Math.max(n, str.length));


var t1 = Math.round(new Date().getTime());
var tmp = leftpad1("233", 10000000, '*');
var t2 = Math.round(new Date().getTime());
console.log(tmp.length);
console.log('leftpad1: ' + String(t2-t1));

var t1 = Math.round(new Date().getTime());
var tmp = leftpad2("233", 10000000, '*');
var t2 = Math.round(new Date().getTime());
console.log(tmp.length);
console.log('leftpad2: ' + String(t2-t1));

var t1 = Math.round(new Date().getTime());
var tmp = leftpad3("233", 10000000, '*');
var t2 = Math.round(new Date().getTime());
console.log(tmp.length);
console.log('leftpad3: ' + String(t2-t1));

var t1 = Math.round(new Date().getTime());
var tmp = leftpad4("233", 10000000, '*');
var t2 = Math.round(new Date().getTime());
console.log(tmp.length);
console.log('leftpad4: ' + String(t2-t1));