What the `Nullish coalescing operator (??)`

Well, you must be wondering what I am going to talk about! Today, I learn about a peculiar operator which modern javascript supports, known as Nullish Coalescing Operator(??).
So what is this operator?
Syntax:

Expression1 ?? Expression2

So, from the above syntax, you can see that

• It is a binary operator( i.e. it requires two operands / expressions ) and
• returns the value of the first expression which is not null or undefined Example:

let age = a ?? b

Here, the age variable will contain the value of a if it is not null or undefined, otherwise, it will contain the value of b.

Well, Basically It turns into the below code

// consider a and b is known
if(a == null || a == undefined)
{
   age = b;
}
else
{
  age = a;
}

NOTE: ?? operator works similar to the || (logical-OR) but the only difference is that the || operator checks for falsy values and ?? checks for the values that are null or undefined

let var1 = 0 ?? 23  // var1 = 0
let var2 = 0 || 23  // var2 = 23

Limitation:

• We can't use this ?? operator with && or || without explicit parantheses. Example:

0 && 2 ?? 3  // Uncaught SyntaxError
( 0 && 2 ) ?? 3 // 0

2nd code works perfectly fine and returns 0 because the code becomes 0 ?? 3 and because 0 is not null or undefined the output is 0. 😉

I Hope, you learnt something new today and will find this useful. As this is my first post on this amazing platform, please spare me, if the post has any error.
Have a good day and night as well 😛

Resources: (for more information)

https://javascript.info/nullish-coalescing-operator
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing_operator