nullish coalescing operator not working code example

Example 1: 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'

Example 2: nullish-coalescing-operator

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

Example 3: nullish-coalescing-operator

let foo = { someFooProp: "hi" };

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