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Run results for: Map vs preallocation vs slice vs spread

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Run details:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.1.2 Safari/605.1.15
Safari 14
Mac OS X 10.15.7
Desktop
3 years ago
Test name Executions per second
Map 259.5 Ops/sec
from 10.0 Ops/sec
splice 313.8 Ops/sec
spread 412.9 Ops/sec
loop 402.5 Ops/sec
Script Preparation code:
AخA
 
var array = Array.from(new Array(1000000), (e, i) => Math.random());
Tests:

  • Map

     
    var array2 = array.map((e, i) => e);

  • from

     
    var array2 = Array.from(new Array(1000000), (e, i) => array[i]);

  • splice

     
    var array2 = array.slice();

  • spread

     
    var array2 = [...array];

  • loop

     
    var array2 = new Array(1000000).fill(0), n=array2.length;
    for (let i = 0; i < n; i++) array2[i] = i;