Run results for: findIndex in map vs. lookup + map

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser: Chrome 119

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
map + findIndex	0.7 Ops/sec
lookup + map	381.6 Ops/sec

Script Preparation code:

var arr1 = [];
var arr2 = [];
var i = 0;
var j = 0;

while (i <= 1E5) {
  arr1[i] = i++;
  arr2[j] = j++;
}

Tests:

map + findIndex
arr1.map((item1) => (arr2.findIndex(item2 => item2 === item1)));
lookup + map
const lookup = arr2.reduce((lookup, item, index) => {lookup[item] = index; return lookup;}, {}); arr2.map((item) => lookup[item]);