JavaScript – ES6 Cheat Sheet

Sedikit catatan dari contoh penggunaan sehari-hari code javascript dengan standard ES6,

Arrow Function

const sum = (a,b) => a + b;
console.log(sum(2,6)) // prints 8

Default Parameters

function print(a = 5) {
   console.log(a)
}

print() // prints 5
print(22) // prints 22

Let Scope

let a = 3
if (true) {
  let a = 5
  console.log(a) // prints 5
}
console.log(a) // prints 3

Const

// can be assigned only once
const a = 55
a = 44 // throws an error

Multi-line String

console.log(
  `This is a
  multi-line string`
)

Template String

const names = "World"
const message = `Hello ${names}`
console.log(message)

// prints "Hello World"

Exponent Operator

const byte = 2 ** 8

// expected result = 256

// Same as: Math.pow(2, 8)

Spread Operator

Ini sama dengan array_merge($arr1,$arr2) pada php

const a = [ 1, 2 ]
const b = [ 3, 4 ]
const c = [ ...a, ...b ]

console.log(c) 

// [1, 2, 3, 4]

String Includes()

console.log('Dankdev'.includes('s'))

// prints true

console.log('Dankdev'.includes('m'))

// prints false



// includes() method ini case sensitive, contohnya 
console.log('Dankdev'.includes('E'))

// prints false

console.log('Dankdev'.includes('D'))
// prints true

String startsWith()

console.log('Dankedev'.includes('Da'))

// prints true

console.log('Dankedev'.includes('an'))

// prints false

String repeat()

console.log('ha'.repeat(3))

// prints "hahaha"

Destructuring array

let [a,b] = [3,7];

console.log(a); // 3
console.log(b); // 7

Destructuring object

let obj = {
  a: 77,
  b: 66
};

let { a,b } = obj;

console.log(a); // 77
console.log(b); // 66

Object Property Assignment

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 }

Object.assign()

const obj1 = { a: 1 }
const obj2 = { b: 2 }

const obj3 = Object.assign({},
      obj1, obj2)

console.log(obj3)
// { a: 1, b: 2 }

Promises with finally

Promise

 .then((result) => { ... })
 .catch((error) => { ... })
 .finally(() => { /* logic independent of success/error */ })

 /* The handler is called when the promise is fulfilled or rejected. */

//biasa dipakai saat menggunakan async dan await pada saat kita melakukan request dengan fetch atau ketika menggunakan axios

Spread Operator

const a = {
  firstName: "Hadie",
  lastName: "Danker",
}

const b = {
   ...a,
  lastName: "Abu Arsy",
  canSing: true,
}

console.log(a)

//{firstName: "Haddide", lastName: "Danker"}


console.log(b)

/* {firstName: "Hadie", lastName: "Abu Arsy",
   canSign: true} */

// cara ampuh untuk memodifikasi object tanpa harus mempengaruhi object aslinya

Destructuring Nested objects

const Person = {
  name: "Hadie Danker",
  age: 17, // :)
  sex: "male",
  maritalstatus: "single",
  address: {
  country: "ID",
  state: "South Sumatrea",
  city: "OKU",
  pincode: "123456",
 },
};

const { address: { state, pincode }, name } = Person;

console.log(name, state, pincode)

// Hadie Danker South Sumatera 123456

console.log(city) // ReferenceError

Object function assignment

const obj = {
  a: 5,
  b() {
  
 console.log('b')

 }
}

obj.b() // prints "b"

Object.entries()

Looping object as array entries

const obj = {
  firstName: "Hadie",
  lastName: "anker",
  age: 17,
  country: "Indonesia",
};

const entries = Object.entries(obj);

console.log(entries)

/* prints [

   ['firstName', 'Hadie'],
   ['lastName', 'Danker'],
   ['age', 23],
   ['country', 'Indonesia']

  ];

*/

Object.keys()

const obj = {
  firstName: "Hadie",
  lastName: "Danker",
  age: 17,
  country: "Indonesia",
};

const keys = Object.keys(obj);

console.log(keys);

/* prints [
'firstName',
'lastName',
'age',
'country'
  ];

*/

Sorting Array

// Sorting Ascending
const arr = [40, 100, 1, 5, 25, 10];
arr.sort((a,b) => a - b)

console.log(arr)
/*
[
    100,
    40,
    25,
    10,
    5,
    1
]
*/


// Sorting Descending
arr.sort((a,b) => b - a)

Sorting Multidimensional Array

	const Categories = [
		{
			id:10,
			name:'PHP'
		},
		{
			id:5,
			name:'JavaScript'
		},
		{
			id:30,
			name:'Go'
		},
	]
	
	// Sorting Ascending
	Categories.sort( (a,b) => a.id - b.id);
	
	console.log(Categories);
	
	
	//Sorting Descending

	Categories.sort( (a,b) => b.id - a.id);

	console.log(Categories);

Demikian catatan singkat tentang cheatset code javascript dengan standard es6 yang biasa saya gunakan. Semoga bermanfaat.