How do I get the actual size in bytes for a number and a string in JavaScript in a browser environment?

Question

I am trying to get the actual size (in bytes) of a number and a string in browsers e.g. chrome.

I learned that in JavaScript numbers are represented in double precision takes up 64 bits and strings are UTF-16 code unit so it takes either 2 bytes or 4 bytes.

I first tried to use new Blob but it encodes string component characters as UTF-8 not UTF-16. And I know there is a Buffer.from API in Node but it is not available in a browser environment.

My question is how I can get the actual size of a number and a string in bytes from a browser, e.g. chrome?

Answer 1

You can do that natively with the help of TextEncoder

let str1 = 'Beta'; // 'Beta' text in English
let str2 = '贝塔'; // 'Beta' text in Chinese

const encoder = new TextEncoder();

const len1 = encoder.encode(str1).length;
const len2 = encoder.encode(str2).length;

console.log(len1); // 4
console.log(len2); // 6

Answer 2

First of all it is important to realize that the spec doesn't mandate any representation. Just behavior.

Strings are stored in UTF-16 but fortunately for your purpose each index represents 16 bits.

For example

console.log('😠'.length); // Should log 2 because emoji takes 2 16 bit parts

For numbers it depends. V8 represents small integer numbers as actual 32 bit ints.