JAVASCRIPT

nullish coalesing

Expression:
	Left ?? Right
if left is null or undefined , then Right will be the value 

const a = '' ;
const b = undefined;

const c = a ?? 'default' ; // will give c =''
const d = b ?? 'default' ; // wil give d = 'default'

Nullish Coalescing Vs Logical OR opreators

console.log(<left-operand> <operator> <right-operand>);

// same behaviour
console.log(undefined || "John");	// "John"
console.log(undefined ?? "John");	// "John"
            
console.log(null || "John");	// "John"
console.log(null ?? "John");	// "John"

// different behaviour
console.log(0 || "John");	// "John"
console.log(0 ?? "John");	// 0
            
console.log("" || "John");	// "John"
console.log("" ?? "John");	// ""

console.log(false || "John");	// "John"
console.log(false ?? "John");	// false

nullish coalescing operator

//nullish coalescing operator in js
Expression:
	Left ?? Right
if left is null or undefined , then Right will be the value

let value = null ?? "Oops.. null or undefined";
console.log(value) //Oops.. null or undefined

value = undefined ?? "Oops.. null or undefined";
console.log(value) //Oops.. null or undefined

value = 25 ?? "Oops.. null or undefined";
console.log(value) // 25

value = "" ?? "Oops.. null or undefined";
console.log(value) // ""

nullish coalescing operator

(null || undefined) ?? "toto"; // Renvoie "toto"

nullish-coalescing-operator

null || undefined ?? "foo"; // raises a SyntaxError
true || undefined ?? "foo"; // raises a SyntaxError

Nullish Coalescing

let x = foo ?? bar(); // return foo if it's not null or undefined otherwise calculate bar

Nullish coalescing operator

alert(username ?? "Guest");

nullish-coalescing-operator

let foo = { someFooProp: "hi" };

console.log(foo.someFooProp?.toUpperCase() ?? "not available"); // "HI"
console.log(foo.someBarProp?.toUpperCase() ?? "not available"); // "not available"