Run results for: Obj vs map for in vs for of

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Browser: Chrome 78

Operating system: Windows

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
map for of	70794.5 Ops/sec
obj for in	4653.4 Ops/sec
map for of kyes	8294611.5 Ops/sec

HTML Preparation code:

<script>
function randomString()
{
    var text = "";
    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

    for( var i=0; i < 5; i++ )
        text += possible.charAt(Math.floor(Math.random() * possible.length));

    return text;
}

var preComputedRandomKeys = [];
var preComputedRandomVals = [];

for (var i=0; i < 1000; i++) {
   preComputedRandomKeys[i] = randomString();
   preComputedRandomVals[i] = randomString();
}
</script>

Script Preparation code:

var map = new Map();
var obj = {};

var map2 = new Map();
var obj2 = {};

for (var i=0; i < 1000; i++) {
   map2.set(preComputedRandomKeys[i], preComputedRandomVals[i]);
   obj2[preComputedRandomKeys[i]] = preComputedRandomVals[i];
}

Tests:

map for of
for (var valit of map2) { var val = valit; }
obj for in
var key; for (key in obj2) { var val = obj2[key]; }
map for of kyes
for (var key in map2) { var val = map2.get(key); }

Run results for: Obj vs map for in vs for of

testing map and object iteration, for in, for of

map for of

obj for in

map for of kyes