Memory Usage Of Different Data Types in javascript

Question

A question that has happened to me is that different Data type in javascript how many use of memory . for Example in C++ data type like int , char , float uses order 2 , 1 ,

Answer 1

As of today, MDN Data Structures page gives some more info about it:

Number

According to the ECMAScript standard, there is only one number type: the double-precision 64-bit binary format IEEE 754 value

So that should amount to 8 bytes.

String

JavaScript's String type is used to represent textual data. It is a set of "elements" of 16-bit unsigned integer values.

So that should amount to 2 bytes per character.

Boolean

Boolean represents a logical entity and can have two values: true, and false.

Nothing more about that.

Answer 2

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.