Run results for: Array creation (preallocated vs from fixed)

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36

Browser: Chrome 116

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Script Preparation code:

var objs = [];
for (var i = 0; i < 1000; i++) {
    objs.push({
        foo: {baz: null},
        bar: null
    });
}
var fieldName = "foo"

Tests:

Array.from
const out = Array.from(objs, (o) => o[fieldName]);
Preallocate null
const out = new Array(objs.length).fill(null); for (let i = 0; i < objs.length; i++) { out[i] = objs[i][fieldName] }
Preallocate 0
const out = new Array(objs.length).fill(0); for (let i = 0; i < objs.length; i++) { out[i] = objs[i][fieldName] }
Preallocate empty object
const out = new Array(objs.length).fill({}); for (let i = 0; i < objs.length; i++) { out[i] = objs[i][fieldName] }
Unfilled initial array
const out = new Array(objs.length); for (let i = 0; i < objs.length; i++) { out[i] = objs[i][fieldName] }