JavaScript Arrow Function

Arrow functions were introduced with ES6 for shorter function syntax

It can be used as Constructor. it also best for non-method function

Syntax

(param1, param2,.., paramN) => { statements } 

Example

var test = () => {
  return "test JS";
}
test();
//output
//test JS

Arrow Function With Single Parameters

var test = (name) => 'Name is '+name;
test('Ashish');
//output
//Name is Ashish

//OR
var test = name => 'Name is '+name;
test('Ashish');
//output
//Name is Ashish

Arrow Function With Multiple Parameters

var sum = (n1,n2) =>{
 return n1+n2;
} 
sum(2,3);
//output
//5

Arrow Function With default Parameters and Hoisting

//default parameter with regular funstion
function testReg(name='Ashish'){
console.log(name);
}
testReg();
//Ashish

//default parameter with arrow funstion
const testArrow = (name='Avanish')=>console.log(name);
testArrow();
//Avanish

//hoisting
testReg();
function testReg(name='Ashish'){
console.log(name);
}
//Ashish

testArrow();
const testArrow = (name='Avanish')=>console.log(name);
//Uncaught ReferenceError: Cannot access 'testArrow' before initialization

Arrow function with return type object

const objectTest = ()=>({name:'Ashish'});
const person=objectTest();
console.log(person);
//output
//{name: "Ashish"}

Arrow Function "this" object example

Example

//ES5
var person = {
name:'Ashish',
age:30,
testHello : function(){ 
	console.log(this.name);
}
}; 
person.testHello();
//Ashish

//ES5
var person = {
name:'Ashish',
age:30,
testHello : function(){ 
var self=this;
	setTimeout(function() {
		console.log(self.name);
	},10);
}
}; 
person.testHello();
//Ashish

//ES6
var person = {
name:'Ashish',
age:30,
testHello : function(){ 
	setTimeout(() => {
		console.log(this.name);
	},10);
}
}; 
person.testHello();
//Ashish


//ES6
var person = {
name:'Ashish',
age:30,
testHello : ()=>{
	console.log(this.name)
 }
}; 
person.testHello();
//undefined