Javascript Function Arrow Function

Introduction

Javascript arrow function is defined as follows: 

let arrowSum = (a, b) => { 
  return a + b; /*from  w  ww. j a v a  2s  . c o  m*/
}; 
//The same function defined in tranditional way.
let functionExpressionSum = function(a, b) { 
  return a + b; 
}; 
  
console.log(arrowSum(5, 8));  // 13  
console.log(functionExpressionSum(5, 8));  // 13

Arrow functions are used inline. 

let ints = [1, 2, 3]; 
console.log(ints.map(function(i) { return i + 1; }));  // [2, 3, 4] 
console.log(ints.map((i) => { return i + 1 }));        // [2, 3, 4]

Arrow functions do not require the parentheses for a single parameter.

To have zero or more than one parameter, parentheses are required: 

// Both are valid 
let double = (x) => { return 2 * x; }; 
let triple = x => { return 3 * x; };

Zero parameters require an empty pair of parentheses 

let getRandom = () => { return Math.random(); };

Multiple parameters require parentheses 

let sum = (a, b) => { return a + b; };

For single line function body we can omit the curly braces.

Both are valid and will return the value 

let double = (x) => { return 2 * x; }; 
let triple = (x) => 3 * x;

Assignment is allowed 

let value = {}; //from www  .j a  v a2s. c  o  m
let setName = (x) => x.name = "CSS"; 
setName(value); 
console.log(value.name);  // "CSS"



PreviousNext

Related