Arrow_Function.js

// Arrow Functions are recommended to use

var add = (x,y) => x+y;  // if code is of single lines then writing return implicitly.

typeof add;
'function'

add(10,20);
30


// Arrow Functions are Pure Function => No this concept, no constructur, no arguments

// Named Functions are not pure functions as they have the ability to create object constructor
function show(){
    console.log(" i am the show ");
}

show();
i am the show 

var e = new show();            // creating object
i am the show 

typeof e;
'object'
e instanceof show;
true
show.constructor;
ƒ Function() { [native code] }
add(10,20);
30


var t = new add(10,20);       // Pure function
VM529:1 Uncaught TypeError: add is not a constructor
    at <anonymous>:1:9
(anonymous) @ VM529:1

add.constructor;        // Property is there but we can't use that property
ƒ Function() { [native code] }
add(10,20);
30


var adder = (x,y)=>{
    console.log(x, y);
    return x + y;    // if code is of multiple lines then writting return explicitly is imp.
}

adder(10,20);
10 20
30

console.dir(show);
VM901:1 ƒ show()arguments: nullcaller: nulllength: 0name: "show"prototype: {constructor: ƒ}[[FunctionLocation]]: VM260:1[[Prototype]]: ƒ ()[[Scopes]]: Scopes[1]
undefined
console.dir(add);
VM948:1 add()length: 2name: "add"arguments: (...)caller: (...)[[FunctionLocation]]: VM60:1[[Prototype]]: ƒ ()[[Scopes]]: Scopes[1]

var myadd = ()=>{
    console.log(arguments.length);
}

function disp(){
    console.log(arguments.length);
}

disp(10,20);           // working fine bcz it's not an Arrow function
VM1202:2 2
undefined
myadd(10,20);        //  this will give error bcz it is an Arrow function, Pure function no concept of arguments.
VM1070:2 Uncaught ReferenceError: arguments is not defined
    at myadd (<anonymous>:2:17)
    at <anonymous>:1:1
myadd @ VM1070:2
(anonymous) @ VM1275:1

var myadd = (...a)=>{           // if we want to pass multiple arguments then we have to use REST method
    console.log(a.length);
}

myadd(10,20,30,40);
4

var g =()=>"Hello";   // writing brackets when there with no argument is compulsory
undefined
g();
'Hello'
var y = x=>x*x;   // writing brackets when there is one argument is optional
undefined
y(10);
100