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Run results for: Extending ArrayBufferView with Properties

How does extending an ArrayBufferView to add properties or functionality affect performance?

Go to the benchmark
Run details:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Firefox/91.0
Firefox 91
Mac OS X 10.15
Desktop
3 years ago
Test name Executions per second
Regular Array 4723.9 Ops/sec
Uint Array 5164.0 Ops/sec
Uint Array Expando 5110.8 Ops/sec
Custom Array 50820496.0 Ops/sec
Custom Uint Array 44522384.0 Ops/sec
Script Preparation code:
​x
 
class CustomArray extends Array {
    constructor(...args) {
        super(...args);
        this.position = 0;
    }
}
​
class CustomUint8Array extends Uint8Array {
    constructor(...args) {
        super(...args);
        this.position = 0;
    }
}
​
const LENGTH = 12000;
​
var rArray = [];
var uint8Array = new Uint8Array(LENGTH);
var uint8ArrayExp = new Uint8Array(LENGTH);
uint8ArrayExp.position = 0;
var cArray = new CustomArray(LENGTH);
var cUint8Array = new CustomUint8Array(LENGTH);
​
for (let i = 0; i < LENGTH; i++) {
    const v = ~~(Math.random() * 255);
    rArray.push(v);
    uint8Array[i] = v;
    uint8ArrayExp[i] = v;
    cArray[i] = v;
    cUint8Array[i] = v;
}
​
console.log(`rArray: ${rArray.length}, uint8Array: ${uint8Array.length}, uint8ArrayExp: ${uint8ArrayExp.length}, cArray: ${cArray.length}, cUint8Array: ${cUint8Array.length}`);
Tests:

  • Regular Array

     
    function read(arr, offset) {
      let pos = offset;
      while (pos < arr.length) {
        pos++;
        if (arr[pos] < 127) {
          return pos;
        }
      }
      return pos;
    }
    ​
    let o = 0;
    while (o < rArray.length) {
      o = read(rArray, o);
    }

  • Uint Array

     
    function read(arr, offset) {
      let pos = offset;
      while (pos < arr.length) {
        pos++;
        if (arr[pos] < 127) {
          return pos;
        }
      }
      return pos;
    }
    ​
    let o = 0;
    while (o < uint8Array.length) {
      o = read(uint8Array, o);
    }

  • Uint Array Expando

     
    function read(arr) {
      while (arr.position < arr.length) {
        arr.position++;
        if (arr[arr.position] < 127) {
          return arr.position;
        }
      }
      return arr.position;
    }
    ​
    let o = 0;
    uint8ArrayExp.position = 0;
    while (o < uint8ArrayExp.length) {
      o = read(uint8ArrayExp);
    }

  • Custom Array

     
    function read(arr) {
      while (arr.position < arr.length) {
        arr.position++;
        if (arr[arr.position] < 127) {
          return arr.position;
        }
      }
      return arr.position;
    }
    ​
    let o = 0;
    while (o < cArray.length) {
      o = read(cArray);
    }

  • Custom Uint Array

     
    function read(arr) {
      while (arr.position < arr.length) {
        arr.position++;
        if (arr[arr.position] < 127) {
          return arr.position++;
        }
      }
      return arr.position;
    }
    ​
    let o = 0;
    while (o < cUint8Array.length) {
      o = read(cUint8Array, o);
    }