Run results for: self-assignment vs. if condition

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36

Browser: Chrome 114

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
if condition	7527238.0 Ops/sec
self-assignment	31347188.0 Ops/sec

Tests:

if condition

const x = {
    foo: []
};
const keys = ["foo", "bar"];

for (const key of keys) {
  if (!Object.prototype.hasOwnProperty.call(x, key)) {
    x[key] = [];
  }
}

​x
 
const x = {    foo: []};const keys = ["foo", "bar"];​for (const key of keys) {  if (!Object.prototype.hasOwnProperty.call(x, key)) {    x[key] = [];  }}

self-assignment

const x = {
    foo: []
};
const keys = ["foo", "bar"];

for (const key of keys) {
  x[key] = x[key] ?? [];
}

 
const x = {    foo: []};const keys = ["foo", "bar"];​for (const key of keys) {  x[key] = x[key] ?? [];}