Rest Parameter in JavaScript ES6

Rest Parameter in JavaScript ES6

Rest Parameter in JS ES6 

Rest parameters is introduced in ES6. use to pass the infinite number of arguments in a function as an array. as last parameter and prefixed with three dots(...). 

function fname (x, y, ...Args)  { //code go here }

Rest parameter Syntax 

Parameter x,y : parameter of function ….Args: The rest parameter to pass any number of arguments to the function.

Important Note 

It creates a standard array of user-supplied values .The only last parameter can be the rest parameter. It can not use with function parameters if it is not the last parameter.

Use of Rest Parameter

function fnrest(x,  y, ...restarg)  { console.log(x,y) console.log(restarg ) } //calling function fnrest ("Ja", "va", "rest", "val", "es", "data")

Output of Last Program 

Ja va [ 'rest', 'val', 'es', 'data' ]

The output of restarg  = 'rest', 'val', 'es', 'data' ] that is an array.

Find Length of Rest parameter

To find the length of the rest parameter operator you can use the .length property

Pass Single argument to Rest Parameter

if We pass a single argument to the rest parameter. Even then also it will return an array

Pass No argument to Rest Parameter

if we pass no argument to the rest parameter .Even then also it will return an array