How to calculate byte length containing UTF8 characters using javascript?

Question

I have textbox, in which the user can enter the characters in ASCII/UTF-8 or a combination of both. Is there any API in javascript which we can calculate the length of string in

Answer 1

As of 2018, the most compatible and reliable way of doing this seems to be with the blob api.

new Blob([str]).size

Even supported in IE10 if anyone uses that anymore.