How numbers are saved in JavaScript ?



On this article, we’ll attempt to perceive how numbers are saved in JavaScript. Like every other programming language, all the information is saved inside the pc within the type of binary numbers 0 and 1. Since computer systems can solely perceive and course of knowledge within the type of 0’s and 1’s.

In JavaScript, there’s typically solely a Quantity as a primitive knowledge sort however the numbers are of the shape Integer and float. So these sorts come underneath the Quantity knowledge sort and are internally saved in line with their totally different codecs relying upon the kind of operation being carried out on them.

Allow us to now perceive how totally different numbers are saved in JavaScript.

Storing of Integer Numbers

Integer: These numbers are additional divided into two sorts 

  • Signed Integers
  • Unsigned Integers.

To retailer unsigned integers easy binary format is used.

Beneath are a number of examples of how totally different unsigned integers are saved in JavaScript.

var a = 4
var b = 78

a will probably be saved within the reminiscence with the worth of:- 100
b will probably be saved within the reminiscence with the worth of:- 1001110

Be aware: This technique fails when engaged on unsigned integers as further knowledge is required to retailer the signal of numbers.

There’s a conference to retailer the leftmost bit as an indication bit and use 0 for constructive and 1 if adverse quantity.

This technique is called Signed Magnitude

The beneath instance illustrates how we’ll retailer the quantity in Signed Magnitude format.

var a = 6
var b = -6

a will probably be saved in reminiscence with the worth of :- 000110
b will probably be saved in reminiscence with the worth of :- 100110

An issue arises after we attempt to carry out addition on these two values. the addition carried out on the binary numbers returns

100110 + 000110 = 101100 // 44

We must always get 0 after we add the 2 numbers however as a substitute, we get 44

An extra enchancment of this technique was carried out and one’s complement illustration was used to retailer the quantity

One’s complement of a quantity is toggling all of the 0’s into 1 and 1’s to 0. Suppose there’s a binary quantity 11001001, then its one’s complement will probably be 00110110. 

Now allow us to perceive how this technique is used to retailer numbers within the reminiscence.

Allow us to suppose the quantity in binary format is 100111, which will probably be handled as a adverse quantity since 1 is the leftmost bit. Now its one’s complement is 011000 which is 24 within the decimal format so we’ll deal with 100111 as -24. 

On this technique, the issue which arose within the earlier technique is partially solved as addition now begins giving appropriate outcomes however there’s nonetheless some exceptions akin to after we add 3 and -2 utilizing this illustration we get incorrect output

3 -> 000011 
-2-> 111101
After addition we get -> 000000 which is +0

Output was anticipated to be 1.

To additional improve this strategy the numbers two complement format was launched

Two’s complement of a quantity is just like One’s complement with one further step that after discovering the one’s complement of the number one is added once more to the consequence.

The 2 enhances within the earlier of 24(011000) will probably be 101000. This quantity when added with the unique quantity 24 we get 000000 as output the place the carry bit is ignored and the arithmetic operation passes.

24 -> 011000
two's complement of 24 -> 101000
Addition provides -> 1000000
// One is ignored as digits upto 6 bits are counted

So -24 will probably be saved as 101000 within the reminiscence


When storing Integers in unsigned bit easy binary format is adopted 

With a view to retailer signed bit integers, the numbers internally will probably be saved as two’s complement in order to extend the storage capability and enhance arithmetic calculation.

Storing of Floating level numbers.

To retailer a float quantity we divide it into three components signal bit, exponent, and mantissa.

  • signal bit: It’s used to point an indication of a quantity with conference as 0 for constructive and 1 for adverse.
  • exponent: It’s the distinction between an actual binary quantity and its normalized type.
  • mantissa: It’s used to retailer the fraction a part of the floating level quantity’s normalized type.

Floating level numbers represented utilizing 32-bit format are known as single precision whereas the numbers represented utilizing 64-bit format are known as double precision

Storage House required for storing quantity in numerous codecs:

  signal  exponent mantissa
single 1 bit 8 bits 23 bits
double 1 bit 11 bits 52 bits

The idea of bias is used within the floating level illustration to characterize adverse numbers too as a substitute of 1’s and two’s complement. Bias is used as a result of comparability turns into tough within the case of floating level numbers with two’s complement representations.

For eg., a standard 6-bit illustration will observe numbers from 000000 to 111111 however IEEE has given a components that may retailer the adverse numbers too. If n is the variety of bits the components will probably be.

bias = 2(n-1) - 1
// Right here n = 6
due to this fact bias = 31

This implies in 6-bit illustration we are able to retailer numbers from -31 to 32 

Allow us to see how the binary quantity 101.101 will probably be represented in scientific notation.

we’ll get 1.01101 * 2^2 

  • Right here, the signal bit is 0  and would be the leftmost bit
  • The exponent is 2. It should point out the gap between the unique binary quantity and the normalized type.
  • The mantissa is the fraction half which will probably be 01101

Storing of Irrational Numbers.

Computer systems are nonetheless incapable to retailer and manipulate irrational numbers in order that they can’t be saved.

How Numbers are saved internally in JavaScript:

Now allow us to perceive how JavaScript internally manages to retailer the numbers. JavaScript doesn’t have a separate format for Integer and Float illustration. It makes use of Numbers for every type of numbers. Inside JavaScript, each quantity is saved as 64 floating-point numbers. In some instances for the arithmetic operation of integers, two’s complement format is used.

Issues with Floating Level Numbers in JavaScript

  • The floating level numbers aren’t at all times correct and provides approximate outcomes.

Instance: On this instance, we’ll attempt to perceive the above downside.


var x = 0.1;

var y = 0.2;


Output: Right here, as a substitute of actual calculation an approximate result’s given for quick efficiency

  • Floating numbers give totally different output relying on their associativity

Instance: We’ll perceive the associativity downside with the instance given beneath.


var x = 0.1;

var y = 0.2;

var z = 0.3



Output: Since floating level calculations are based mostly on rounding, due to this fact, the consequence shouldn’t be at all times the identical despite the fact that it must be the identical in real-world purposes.