ES2020 summary

es2020

/* 1. BigInt */

conosle.log(typeof 22n); // bigint
console.log(25n > 20); // true
console.log("1" + 10n); // "11"
console.log(34n.toString()); // "34"
console.log(2n == 2) //true
console.log(2n === 2) //false

/* 2. Promise.allSettled() */

// Output will be array of resolved and rejected objects
Promise.allSettled([
    new Promise(res => setTimeout(() => res(1), 3000)),
    new Promise((res, rej) => setTimeout(() => rej(new Error("Oops")), 5000)),
    new Promise(res => setTimeout(() => resolve(3), 1000))
]).then(data => console.log(data));

Output -
[
  { status: 'fulfilled', value: 1 },
  {
    status: 'rejected',
    reason: Error: oops
        .....
		.....
  },
  { status: 'fulfilled', value: 3 }
]

// All resolved, otherwise only rejected promise.
Promise.all([
    new Promise(res => setTimeout(() => res(1), 3000)),
    new Promise((res, rej) => setTimeout(() => rej(new Error("Oops")), 5000)),
    new Promise(res => setTimeout(() => resolve(3), 1000))
]).then(data => console.log(data));

/* 3. Nullish Coalescing (??) */

// Strictly checks for undefined.
console.log(undefined || "1"); // "1"
console.log(undefined ?? "1"); // "1"
console.log(0 || "1"); // "1"
console.log(0 ?? "1"); // 0

/* 4. Optional chaining (?) */

// Access deeply nested object properties without worrying about reference error.
const response = {
	first: {
		second: { 
			third: "this you want to access"
		}
	}
}
console.log(first.otherSecond.third); //Reference error
console.log(first?.otherSecond?.third); //undefined

/* 5. globalThis */

globalThis.log = "This will be accessible everywhere".

/* 6. Dynamic import */

//print.js
const print = (value) => `Hi ${value}`
export { print };

//greet.js
const greet = value => import('./print.js).then(func => func(value));
greet("sunny"); //Hi sunny

/* 7.String.prototype.matchAll() */
// Replacement of regex.exec(). Returns iterator.
const regexp = RegExp('[a-z]*ame','g');
const str = 'rame suot name vjaoi game';
let match;
while ((match = regexp.exec(str)) !== null) {
  console.log(match)
}
// Same as
console.log(...str.matchAll(regexp));