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Declaring variables

// Longhand
let x;   
let y = 20;   

// Shorthand
let x, y = 20;   

Assigning values to multiple variables

// Longhand
let a, b, c; 
a = 5; 
b = 8; 
c = 12;

// Shorthand
let [a, b, c] = [5, 8, 12];

The Ternary operator

// Longhand
let result; 
let marks = GetNumber(); 
if(marks >= 56){
 result = 'Pass'; 
}else{ 
 result = 'Fail'; 
} 

// Shorthand
let result = GetNumber() >= 56 ? 'Pass' : 'Fail'; 

AND(&&) Short circuit evaluation

// Longhand
if (isLoggedin) {
 goToHomepage(); 
} 

// Shorthand
isLoggedin && goToHomepage();

Swap two variables

let x = 'Hello', y = 55; 

// Longhand
const temp = x; 
x = y; 
y = temp; 

// Shorthand
[x, y] = [y, x];

Assigning default value

// Longhand
let imagePath; 
let path = getImagePath(); 
if(path !== null && path !== undefined) { 
  imagePath = path; 
} else { 
  imagePath = 'default.jpg'; 
} 

// Shorthand
let imagePath = getImagePath() || 'default.jpg';

Arrow Function

// Longhand
function add(num1, num2) { 
   return num1 + num2; 
} 

// Shorthand
const add = (num1, num2) => num1 + num2;

Reference: JavaScript Arrow function

Object Property Assignment

let firstname = 'John';
let lastname = 'Doe';

// Longhand
let obj = {firstname: firstname,
           lastname: lastname};

// Shorthand
let obj = {firstname, lastname};

Multi-line String

// Longhand
console.log('JavaScript, often abbreviated\n' +
'as JS, is a programming language that \n' + 
'conforms to the ECMAScript specification. \n' + 
'JavaScript is high-level, often \n' + 
'just-in-time compiled, and multi-paradigm.' ); 

// Shorthand
console.log(`JavaScript, often abbreviated 
as JS, is a programming language that 
conforms to the ECMAScript specification. 
JavaScript is high-level, often 
just-in-time compiled, and multi-paradigm.`);

String into a Number

// Longhand
let total = parseInt('453');
let average = parseFloat('42.6');

// Shorthand
let total = +'453'; 
let average = +'42.6';

Double NOT bitwise operator (~~)

// Longhand
const floor = Math.floor(6.8); // 6 

// Shorthand
const floor = ~~6.8; // 6

Reference: Math.floor()

Repeat a string for multiple times

// Longhand
let str = ''; 
for(let i = 0; i < 5; i ++) { 
  str += 'Hello '; 
} 
console.log(str); // Hello Hello Hello Hello Hello 

// Shorthand
'Hello '.repeat(5);

Find max and min number in array

const arr = [2, 8, 15, 4]; 

// Longhand
let min = 100, max = 0
for(let i = 0; i < arr.length ; i ++) { 
  if(i >= max){
    max = i;
  }
  if(i <= min){
    min = i;
  }
}

// Shorthand
Math.max(...arr); // 15 
Math.min(...arr); // 2

For loop

let arr = [10, 20, 30, 40]; 

// Longhand
for (let i = 0; i < arr.length; i++) { 
  console.log(arr[i]); 
} 

// Shorthand
for (const val of arr) { 
  console.log(val); 
}

// Shorthand
for (const index in arr) { 
  console.log(`index: ${index},
               value: ${arr[index]}`); 
}

Template Literals

// Longhand
console.log('Call from ' + number + ' at ' + time);

// Shorthand
console.log(`Call from ${number} at ${time}`);

Get character from string

let str = 'Hello world'; 

// Longhand
str.charAt(2); // e

// Shorthand
str[2]; // e

Exponent Power

// Longhand
const power = Math.pow(4, 3); // 64 

// Shorthand
const power = 4**3; // 64

Merging of arrays

let arr = [20, 30]; 

// Longhand
let arr2 = arr.concat([60, 80]); 
// [20, 30, 60, 80] 

// Shorthand
let arr2 = [...arr, 60, 80]; 
// [20, 30, 60, 80]

Loop in object

let obj = {x: 20, y: 50};

// Longhand
const objectArray = Object.keys(obj);
for (let i = 0; i < objectArray.length; i++) { 
  console.log(obj[objectArray[i]]); 
} 

// Shorthand
for (const key in obj) { 
  console.log(obj[key]); 
}

Multiple condition checking

// Longhand
if (value === 1 ||
    value === 'one' ||
    value === 2 || 
    value === 'two') { 
     // Execute some code 
} 

// Shorthand
if ([1, 'one', 2, 'two'].indexOf(value) >= 0) { 
    // Execute some code 
}

// Shorthand
if ([1, 'one', 2, 'two'].includes(value)) { 
    // Execute some code 
}

Deep cloning of multi-level object

let obj = {x: 20, y: {z: 30}}; 

// Longhand
const makeDeepClone = (obj) => { 
  let newObject = {}; 
  Object.keys(obj).map(key => { 
    if(typeof obj[key] === 'object'){ 
      newObject[key] = makeDeepClone(obj[key]); 
    } else { 
      newObject[key] = obj[key]; 
    } 
  }); 
 return newObject; 
} 
const cloneObj = makeDeepClone(obj); 

// Shorthand
const cloneObj = JSON.parse(JSON.stringify(obj));

//Shorthand for single level object
let obj = {x: 20, y: 'hello'};
const cloneObj = {...obj};