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 , 8 byte of memory . now data Type like Number , string , boolean , null , undefind and Objects , Arrays in javascript how many use of memory and what is ranges that accepted ? Accept my apologize because of my low English level!!!

Answer 1

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.

Answer 2

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.