Run results for: splice vs spread operator for adding elements into very large 2D arrays

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0

Browser: Firefox 91

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
splice	24596.8 Ops/sec
spread	156.7 Ops/sec

Script Preparation code:

var arr = []; 
for (let i = 0; i < 4000; i++) {
  arr.push(Array.from({length: 40}, () => Math.floor(Math.random() * 40)));
}

Tests:

splice
arr.splice(3000, 0, [5, 4, 8, 21, 16, 22, 18, 38, 19, 16, 37, 28, 17, 17, 29, 34, 38, 8, 39, 2, 12, 16, 12, 6, 9, 33, 6, 1, 39, 9, 39, 15, 26, 32, 34, 31, 11, 14, 29, 4]);
spread
arr = [ ...arr.slice(0,3000), [5, 4, 8, 21, 16, 22, 18, 38, 19, 16, 37, 28, 17, 17, 29, 34, 38, 8, 39, 2, 12, 16, 12, 6, 9, 33, 6, 1, 39, 9, 39, 15, 26, 32, 34, 31, 11, 14, 29, 4], ...arr.slice(3000) ];