Run results for: Unique elements of two arrays

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.166 Safari/537.36

Browser: Chrome 91

Operating system: Linux

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
Set + spread	347.9 Ops/sec
Set + Array.from	348.3 Ops/sec
Concat + spread	288.5 Ops/sec
lastIndexOf	65.0 Ops/sec

Script Preparation code:

var array1 = [];
for (let i = 0; i < 100000; i++) {
   array1.push(Math.floor((Math.random() * 10) + 1));
}
var array2 = [];
for (let i = 0; i < 100000; i++) {
   array2.push(Math.floor((Math.random() * 10) + 1));
}

Tests:

Set + spread
const uniqueValues = (arr1, arr2) => { const values = new Set(arr1) for(const value of arr2) { values.add(value) } return [...values] } uniqueValues(array1, array2)
Set + Array.from
const uniqueValues = (arr1, arr2) => { const values = new Set(arr1) for(const value of arr2) { values.add(value) } return Array.from(values) } uniqueValues(array1, array2)
Concat + spread
const uniqueValues = (arr1, arr2) => { return [...new Set(arr1.concat(arr2))] for(const value of arr2) { values.add(value) } return [...values] } uniqueValues(array1, array2)
lastIndexOf
const uniqueValues = (arr1, arr2) => { const array = arr1.concat(arr2) return array.filter((item, index) => array.lastIndexOf(item) != index); } uniqueValues(array1, array2)

Run results for: Unique elements of two arrays

Set + spread

Set + Array.from

Concat + spread

lastIndexOf