Junior Front-End Developer
JavaScript ES6 (also known as ECMAScript 2015 or ECMAScript 6) is the newer version of JavaScript that was introduced in 2015. ECMAScript is the standard that the JavaScript programming language uses. ECMAScript provides the specification on how JavaScript programming language should work.
const sum = (a, b) => a + b
console.log(sum(2, 6)) // prints 8
const a = 2
const b = 5
const obj = { a, b }
// Before es6:
// obj = { a: a, b: b }
console.log(obj)
// prints { a: 2, b: 5 }
const obj = {
a: 5,
b() {
console.log('b')
}
}
function print(a = 5) {
console.log(a)
}
print() // prints 5
print(22) //prints 22
let a = 3
if (true) {
let a = 5
console.log(a) // prints 5
}
console.log(a) // prints 3
const obj1 = { a: 1 }
const obj2 = { b: 2 }
const obj = object.assing( {} ,
obj1, obj2)
console.log(obj3)
// { a: 1, b: 2 }
const obj = {
firstname: 'firstname' ,
lastname: 'lastname' ,
age: 24,
country: 'India',
};
const entries = object.entries(obj);
/* returns an array of [key, value]
pairs of the object passed */
console.log(entries);
/* prints
[
['firstname', 'FirstName'],
['lastname', 'LastName'],
['age', 24],
['country', 'India']
]; */
// can be assigned only once
const a = 55
a = 44 // throws an error
promise
.then((result) => { . . .})
.catch((error) => {. . .})
.finally(() => { /* logic
independent of success/error */ })
/* The handler is called when the
promise is fulfilled or rejected.*/
console.log(`
This is a
multiline string
`)
const name = 'world'
const message = `Hello ${name}`
console.log(message)
// prints "Hello World"
const a = {
firstname: "FirstName",
lastname: "LastName",
}
const b = {
. . . a,
lastname: "LastName2",
canSing: true,
}
console.log(a)
//{firstname: "FirstName , lastname: "LastName1"}
console.log(b)
/* {firstname: "FirstName , lastname: "LastName2",
canSing = true} */
*/ great for modifying objects without side
effects/affecting the original */
const byte = 2 ** 8
// same as: Math.pow(2, 8)
const a = [ 1, 2 ]
const b = [ 3, 4]
const c = [ . . . a, . . . b ]
console.log(c) // [1, 2, 3, 4]
console.log('apple' .includes('pl'))
// prints true
console.log('apple' .includes('tt'))
// prints false
console.log('apple'.startsWith('ap'))
//prints true
console.log('apple'.startsWith('bb'))
//prints false
console.log('ab'.repeat (3))
//prints "ababab"
let [a, b] = [3, 7];
console.log(a); // 3
console.log(b); // 7
let obj = {
a: 55,
b: 44
};
let { a, b } = obj;
console.log(a); // 55
console.log(b); // 44
const Person = {
name: "Harry Potter",
age: 29,
sex: "male",
materialStatus: "single",
address : {
country: "USA"
state: "Nevada",
city: "Carson City",
pinCode: "500014",
},
};
const { address : { state, pincode }, name } - Person;
console.log(name, state, pinCode)
// Harry Potter Nevada 500014
console.log(city) // ReferenceError