Run results for: TextDecoder compared to String.fromCharCode

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser: Chrome 135

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

TextDecoder, subarray

5.5M/s

TextDecoder, new uint8array

5.5M/s

String.fromCharCode, subarray

124K/s

View exact numbers

Test name	Executions per second
✓ TextDecoder, subarray	5,533,316 Ops/sec
TextDecoder, new uint8array	5,508,155 Ops/sec
String.fromCharCode, subarray	123,794 Ops/sec

Script Preparation code:

const testLength = 1000;
const startSlice = 300;
const endSlice = 700;

const getRandomCharCode = () => Math.floor(Math.random() * 26) + 97; // a-z letters
const bytes = Array.from({length: testLength}, () => getRandomCharCode());

var buffer = new Uint8Array(bytes);
var decoder = new TextDecoder(); // default 'utf-8' or 'utf8'

Tests:

String.fromCharCode, subarray
String.fromCharCode(...buffer.subarray(startSlice, endSlice));
TextDecoder, new uint8array
const slice = new Uint8Array(buffer.buffer, startSlice, endSlice - startSlice); decoder.decode(slice);
TextDecoder, subarray
decoder.decode(buffer.subarray(startSlice, endSlice))