Today I Learned - Rocky Kev

TIL why emojis in JS counts as a length of 2

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TAGS: javascript fonts

You can put emojis in code.

Take a look at this:

const smile = '😀';

smile.length; // => 2

Why is it a length of 2?

It’s because JavaScript considers strings as a sequence of code units, rather than a sequence of visible characters

The Javascript Specs:

The String type is the set of all ordered sequences of zero or more 16-bit unsigned integer values (“elements”). The String type is generally used to represent textual data in a running ECMAScript program, in which case each element in the String is treated as a UTF-16 code unit value.

Look at that word code unit.
That means every symbol/character is a code unit from 0x0000 until 0xFFFF.

Another key word is UTF-16s. We're talk about that later.

const letter = '\u0048';

letter === 'H' // => true

The grinning face character '😀', which would have the code unit of 0x1F600 (the number 0x1F600 is bigger than 0xFFFF thus doesn’t fit into 16 bits), is encoded with a sequence of 2 code units 0xD83D0xDE00.

Via
https://dmitripavlutin.com/what-is-string-in-javascript/

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