Benchmark cycles: var / let / const

benchmark-cycles-var-let-const.js

/******************************************************************************/
'use strict';
/******************************************************************************/
// via https://twitter.com/bmeurer/status/821804688454680576

console.log(`
  // v8 ${process.versions.v8} (Node.js ${process.versions.node})
`);

function forVar_______(a) {
  var x = 0;
  for (var i = 0, l = a.length; i < l; ++i) x += a[i];
  return x;
}
function forLet_______(a) {
  let x = 0;
  for (let i = 0, l = a.length; i < l; ++i) x += a[i];
  return x;
}

function forOfVar_____(a) {
  var x = 0;
  for (var y of a) x += y;
  return x;
}
function forOfLetConst(a) {
  let x = 0;
  for (const y of a) x += y;
  return x;
}

function forEachVar___(a) {
  var x = 0;
  a.forEach((y) => { x += y; });
  return x;
}
function forEachLet___(a) {
  let x = 0;
  a.forEach((y) => { x += y; });
  return x;
}

const a = [];
for (let i = 0; i < 1000; ++i) a[i] = i;

function bench(f) {
  for (let i = 0; i < 1000; ++i) f.call(null, a);
}

for (let i = 0; i < 10; ++i) {
  bench(forVar_______);
  bench(forLet_______);
  bench(forOfVar_____);
  bench(forOfLetConst);
  bench(forEachVar___);
  bench(forEachLet___);
}

console.time(forVar_______.name);
bench(forVar_______);
console.timeEnd(forVar_______.name);

console.time(forLet_______.name);
bench(forLet_______);
console.timeEnd(forLet_______.name);

console.time(forOfVar_____.name);
bench(forOfVar_____);
console.timeEnd(forOfVar_____.name);

console.time(forOfLetConst.name);
bench(forOfLetConst);
console.timeEnd(forOfLetConst.name);

console.time(forEachVar___.name);
bench(forEachVar___);
console.timeEnd(forEachVar___.name);

console.time(forEachLet___.name);
bench(forEachLet___);
console.timeEnd(forEachLet___.name);

Table: https://gist.github.com/chicoxyzzy/0ecb281f61120a4704d3313e4d600859#gistcomment-1975047