(raw notes)
Nullish coalescing operator (??)

if the left side operand is NULL or UNDEFINED, the right-hand side operand is returned.
const foo = null ?? 'default string'; console.log(foo); // Expected output: "default string"

Nullish values are : NULL and Undefined

Falsey values, these below are the only falesy values in JS

Some more examples
false ?? "llo" -> since the left hand side operand is not a nullish value -> so the left hand side value is returned

\=> false

false || "llo" -> here the left side value is a falsey value so the right hand side value will be returned

\=>"llo"

Value	Type	Description
null	Null	The keyword `null` — the absence of any value.
undefined	Undefined	`undefined` — the primitive value.
`false`	Boolean	The keyword `false`.
NaN	Number	`NaN` — not a number.
`0`	Number	The `Number` zero, also including `0.0`, `0x0`, etc.
`-0`	Number	The `Number` negative zero, also including `-0.0`, `-0x0`, etc.
`0n`	BigInt	The `BigInt` zero, also including `0x0n`, etc. Note that there is no `BigInt` negative zero — the negation of `0n` is `0n`.
`""`	String	Empty string value, also including `''` and `` .
`document.all`	Object	The only falsy object in JavaScript is the built-in `document.all`.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing

Nullish coalescing operator (??) vs OR(||)

Subscribe to my newsletter

Dheeraj Malik

Dheeraj Malik