Run results for: Testing leftpad just for lulz

Run details:

User agent: Mozilla/5.0 (Android 10; Mobile; rv:132.0) Gecko/132.0 Firefox/132.0

Browser: Firefox Mobile 132

Operating system: Android

Device Platform: Mobile

Date tested: one year ago

string repeat

5K/s

Built-in method

5K/s

Old npm leftpad

2K/s

View exact numbers

Test name	Executions per second
✓ string repeat	5,116 Ops/sec
Built-in method	5,021 Ops/sec
Old npm leftpad	1,746 Ops/sec

Script Preparation code:

function randstring() {
  const l = Math.ceil(Math.random()*16+5)
  const alphabet = "abcdefghijklmnopqrstuvwxyz"
  let a = []
  for (let i=0; i<l; i++) {
     a.push(alphabet[Math.floor(Math.random()*alphabet.length)])
  }
  
  return a.join("")
}

var strings = []
var numbers = []
for (let i=0; i<100; i++) {
  strings.push(randstring())
  numbers.push(Math.floor(Math.random()*10000))
}
var testdata = [strings, numbers]

var leftpad1 = function(str, len, ch) {
  str = str.toString();
  var i = -1;
  if (!ch && ch !== 0) ch = ' ';
  len = len - str.length;
  while (++i < len) {
    str = ch + str;
  }
  return str;
}

var leftpad2 = function(str, len, ch) {
  str = str.toString()
  if (str.length >= len) return str
  
  ch = !ch && ch !== 0 ? " " : ch
  return ch.repeat(len-str.length) + str
}

Tests:

Old npm leftpad
let result = testdata.map( (data) => data.map( (value) => leftpad1(value, 50)))
string repeat
let result = testdata.map( (data) => data.map( (value) => leftpad2(value, 50)))
Built-in method
let result = testdata.map( (data) => data.map( (value) => value.toString().padStart(50)))