Numbers are 8 bytes.

Found that in this w3schools page.

I searched around a bit more for other JavaScript primitive types, but it's surprisingly hard to find this information! I did find the following code though:

    ...

    if ( typeof value === 'boolean' ) {

        bytes += 4;

    }

    else if ( typeof value === 'string' ) {

        bytes += value.length * 2;

    }

    else if ( typeof value === 'number' ) {

        bytes += 8;

    }

    ...

Seems to indicate that a String is 2 bytes per character, and a boolean is 4 bytes.

Found that code here and here. The full code's actually used to get the rough size of an object.

Although, upon further reading, I found this interesting code by konijn on this page: Count byte length of string.

function getByteCount( s )

{

  var count = 0, stringLength = s.length, i;

  s = String( s ||  );

  for( i = 0 ; i < stringLength ; i++ )

  {

    var partCount = encodeURI( s[i] ).split(%).length;

    count += partCount==1?1:partCount-1;

  }

  return count;

}

getByteCount(i♥js); // 6 bytes

getByteCount(abcd); // 4 bytes

So it seems that the string's size in memory depends on the characters themselves. Although I am still trying to figure out why he set the count to 1 if it's 1, otherwise he took count-1 (in the for loop).

Will update post if I find anything else.