How to get string size in bytes in javascript(examples)

Different ways to find string size or length in bytes In Javascript

  • nodejs buffer object, an example is Buffer.byteLength("str", 'utf8'))
  • Using Blob object, new Blob([str]).size
  • TextEncoder encoder method, new TextEncoder().encode(str).length
  • unescape method,unescape(encodeURIComponent(str)).length

A string in JavaScript is a group of characters, Each character holds 16 bits of an integer. Each string stores the data in memory, as we don’t have a direct method like sizeof in a c programming language.

You can check my other post on Javascript check substring exists in a String Let’s declare the input string.

var str = "a";
var str1 = "ab";
var str2 = "aabc";
var str3 = "πŸ™‚";
var str4 = "πŸ‘πŸ™‚";

input one character returns 1 byte in characters, whereas β€œab” returns 2 bytes. However, emojis return 4 bytes for each symbol, and two emojis return 8 bytes.

Emojis are UTF encoding strings that use 4 bytes to represent a character.

The output of the above input is


Use nodejs buffer object

BufferπŸ”— is an inbuilt object in NodeJS programming, used to store the fixed bytes.

Buffer’s byteLength method returns string size in bytes with a given encoding.

Here is a syntax

Buffer.byteLength(String, encoding);
  • String - string raw data
  • encoding - UTF-8 or UTF-16

It returns String size in bytes.

console.log(Buffer.byteLength(str, "utf8")); // 1
console.log(Buffer.byteLength(str1, "utf8")); // 2
console.log(Buffer.byteLength(str2, "utf8")); // 4
console.log(Buffer.byteLength(str3, "utf8")); // 4
console.log(Buffer.byteLength(str4, "utf8")); // 8

This approach works in the latest browsers and is widely used on the Client and server side.

Use Blob object

BlobπŸ”— is a javascript inbuilt object, used to get binary data of any type of file.

The file can be images or string text. Create a Blob object using String, called Blob.size property returns the size of a string.

console.log(new Blob([str]).size); // 1
console.log(new Blob([str1]).size); // 2
console.log(new Blob([str2]).size); // 4
console.log(new Blob([str3]).size); // 4
console.log(new Blob([str4]).size); // 8

Use TextEncoder encode function

TextEncoderπŸ”— is a function used by web workers to return the string data in bytes The encode method returns the encoded object and the length returns in bytes

console.log(new TextEncoder().encode(str).length);
console.log(new TextEncoder().encode(str1).length);
console.log(new TextEncoder().encode(str2).length);
console.log(new TextEncoder().encode(str3).length);
console.log(new TextEncoder().encode(str4).length);

Use the unescape length method

unescapeπŸ”— is an object going to be deprecated. It is used in encoding the string.

However, the length method of the unescape object can return the string data in bytes.



To Sum Up, There are several methods documented in this post to return the string size in bytes. You can choose the appropriate one based on your needs.