Calculate the byte size of a JavaScript string

Calculating the byte size of a string is surprisingly tricky, especially when dealing with Unicode characters. The length of a string in JavaScript is the number of 16-bit code units in the string, which is not the same as the number of bytes. This is especially important when working with non-ASCII characters, which can be represented by multiple bytes.

In order to correctly handle all cases, we can convert the string into a Blob object, and then use the Blob.size property to get the byte size of the string.

const byteSize = str => new Blob([str]).size;

const helloWorldString = 'Hello World';
helloWorldString.length; // 11
byteSize(helloWorldString); // 11

const emojisString = '😀';
emojiString.length; // 2
byteSize(emojisString); // 4