How many bytes in a JavaScript string?

javascript string size byte
Paul Biggar picture Paul Biggar · Feb 8, 2010 · Viewed 106.6k times · Source

I have a javascript string which is about 500K when being sent from the server in UTF-8. How can I tell its size in JavaScript?

I know that JavaScript uses UCS-2, so does that mean 2 bytes per character. However, does it depend on the JavaScript implementation? Or on the page encoding or maybe content-type?

Answer

Lauri Oherd picture Lauri Oherd · Aug 30, 2012

This function will return the byte size of any UTF-8 string you pass to it.

function byteCount(s) {
    return encodeURI(s).split(/%..|./).length - 1;
}

Source

JavaScript engines are free to use UCS-2 or UTF-16 internally. Most engines that I know of use UTF-16, but whatever choice they made, it’s just an implementation detail that won’t affect the language’s characteristics.

The ECMAScript/JavaScript language itself, however, exposes characters according to UCS-2, not UTF-16.

Source

Related questions

How to check whether a string contains a substring in JavaScript?

Usually I would expect a String.contains() method, but there doesn't seem to be one. What is a reasonable way to check for this?

Read More
How to replace all occurrences of a string?

I have this string: "Test abc test test abc test test test abc test test abc" Doing: str = str.replace('abc', ''); seems to only remove the first occurrence of abc in the string above. How can I replace all …

Read More
How do I make the first letter of a string uppercase in JavaScript?

How do I make the first letter of a string uppercase, but not change the case of any of the other letters? For example: "this is a test" -> "This is a test" "the Eiffel Tower" -> "The …

Read More