How do I get the actual size in bytes for a number and a string in JavaScript in a browser environment?

I am trying to get the actual size (in bytes) of a number and a string in browsers e.g. chrome.

I learned that in JavaScript numbers are represented in double precision takes up 64 bits and strings are UTF-16 code unit so it takes either 2 bytes or 4 bytes.

I first tried to use new Blob but it encodes string component characters as UTF-8 not UTF-16. And I know there is a Buffer.from API in Node but it is not available in a browser environment.

My question is how I can get the actual size of a number and a string in bytes from a browser, e.g. chrome?

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