benchmark of String.startsWith equivalents in Node.js

benchmark-startswith.js

var Benchmark = require('benchmark');
Benchmark.prototype.setup = function() {
  a = ["test"];
  for (var i = 0; i < 10000; i++) {
    a.push("some other stuff");
  }
  s = a.join();
  re1 = new RegExp("^test");
  re2 = new RegExp("^not there");
};
var suite = new Benchmark.Suite();

// add tests
suite.add('indexOf', function() {
  var r1 = (s.indexOf("test") === 0);
  var r2 = (s.indexOf("not there") === 0);
})
  .add('lastIndexOf', function() {
  var r1 = (s.lastIndexOf("test", 0) === 0);
  var r2 = (s.lastIndexOf("not there", 0) === 0);
})
  .add('substring', function() {
  var r1 = (s.substring(0, "test".length) == "test");
  var r2 = (s.substring(0, "not there".length) == "not there");
})
  .add('slice', function() {
  var r1 = (s.slice(0, "test".length) == "test");
  var r2 = (s.slice(0, "not there".length) == "not there");
})
  .add('regex', function() {
  var r1 = (/^test/).test(s);
  var r2 = (/^not there/).test(s);
})
  .add('compiled regex', function() {
  var r1 = re1.test(s);
  var r2 = re2.test(s);
})
// add listeners
.on('cycle', function(event) {
  console.log(String(event.target));
})
  .on('complete', function() {
  console.log('Fastest is ' + this.filter('fastest').pluck('name'));
})
// run async
.run({
  'async': false
});

How to run this via command line?

$ time node starts-with.js

indexOf:
startsWith:
lastIndexOf:
substring:
slice:
regex:
compiled regex:
>Fastest is

node starts-with.js  0.10s user 0.01s system 99% cpu 0.117 total

You can use repeat() to multiply a string

> 'abc'.repeat(100)

'abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc'

I had to use simplification method

var str_repeat = 100
var checks = 1000000

var start = 'start text'
var not_there = 'not there'

var str = start + 'some string'.repeat(str_repeat)

console.time()

for (let i = 0; i < checks; i++)    
    str.startsWith(start)

console.timeEnd()

$ time node starts-with.js

default: 63.477ms
node starts-with.js  0.09s user 0.01s system 98% cpu 0.100 total