Run results for: for..of against Map.entries vs for..in

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.96 Safari/537.36 Edg/88.0.705.56

Browser: Chrome 88

Operating system: Mac OS X 10.15.5

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
for..of Object.entries()	3368.4 Ops/sec
for..in	10594060.0 Ops/sec
for..of Object.entries() no destructuring	3715.6 Ops/sec

Script Preparation code:

var array = Array.from({ length: 10000 }, () => {
  const n = Math.floor(Math.random() * 100)
  if (n > 26) {
    return n
  } else {
    return String.fromCharCode('a'.charCodeAt(0) + n);
  }
});
var obj = new Map();
for (let i = 0; i < array.length; i++) {
  obj.set(i, array[i]);
}

Tests:

for..of Object.entries()
for (const [key, val] of obj.entries()) { const foo = val + 'a'; }
for..in
for (const key in obj.entries()) { const val = obj[key]; const foo = val + 'a'; }
for..of Object.entries() no destructuring
for (const entry of obj.entries()) { const key = entry[0]; const val = entry[1]; const foo = val + 'a'; }

Run results for: for..of against Map.entries vs for..in

for..of Object.entries()

for..in

for..of Object.entries() no destructuring