Run results for: perf check

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Browser: Chrome 86

Operating system: Mac OS X 10.14.6

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
1	621.3 Ops/sec
2	671.9 Ops/sec

Script Preparation code:

var nested = Array.from({
    length: 10000
}).map(() => Math.floor(Math.random() * Math.floor(10)));
var list = [2,3,4,5];

AخA
 
var nested = Array.from({    length: 10000}).map(() => Math.floor(Math.random() * Math.floor(10)));var list = [2,3,4,5];

Tests:

nested.map(item => {
  if (list.indexOf(item) === -1) {
    list.push(item);
  }
});

 
nested.map(item => {  if (list.indexOf(item) === -1) {    list.push(item);  }});

const selectedNested = nested.filter(item => list.indexOf(item) === -1);
list = list.concat(selectedNested);

 
const selectedNested = nested.filter(item => list.indexOf(item) === -1);list = list.concat(selectedNested);