DAY 9 - JULY 30

FUNCTION

BASIC FUNCTION SYNTAX

function  f.name(parameter)

{

}

EVERY TIME WE NEED TO CALL/INVOKE THE FUNCTION

function add(a, b) {

  

   console.log(a + b)

}

 var a = add; // function add(a, b)

 var b = add(3,5) //8

console.log / return inside function

function add(a, b) {

      console.log(a + b)

a - b

}

Console.log(a+b) will display the output directly

If u want to use the output of this function as data for other line u need to use return .

If we use both it will print console and log immediately and store the return value in the variable

return RELATED PROBLEMS

PROBLEM 1

function myfun(a, b) {

    console.log("hi");

    if (a == 10) {

        return a - b;

    }

    console.log(a + b);

    return a + b;

    console.log("hello");

}

a1 = myfun(10, 20);

console.log(a1); //hi -10

b1 = myfun(20, 10);

console.log(b1); // hi 30 30

PROBLEM 2

var m1 = 10;

m1 = 20;

function f1(m1)

{

if(m1 == 10)

{

  m1 = 20;

   return 30;

}

if(m1 == 11)

{

  return;

}

return 30;

console.log(m1);

}

m1 = f1(10);

console.log(m1); //30

m1 = f1(11);

console.log(m1); // undefined

If Parameter Count < Argument Count then the remaining parameters are consider as undefined

If Parameter Count  > Argument Count then the remaining parameters are omitted

Because of this Function Overloading is not possible in JavaScript

function add(a, b,c) {

    

    return a +b+c

}

 var a =10,20,30)//60

 var b = 10) //NaN (10+undefined+undefined)

FUNCTION OVERLOADING

 

function add (a,b,c)

function add (inta,intb)

function add (inta,intb)

In above case if user gives only two inputs a, b then automatically JavaScript take value c as undefined and automatically execute the first add thats why Function Over Loading is not possible in JavaScript

DEFAULT PARAMETER

In javascript we can able to set only the last parameter as default parameter we can’t set first or middle parameter as default parameter.

function add(a=10,b,c) {

    

    return a+b+c

}

 var a = add(20,30)// 20+30+undefined = NaN

 function add(a,b,c=10) {

    

    return a+b+c

}

 var a = add(20,30)// 20+30+10 =60

ANONYMOUS FUNCTION

Function without name and passed inside the variable.To call this function we need to call the variable

var add =function(a,b,c) {

    

   return a+b+c

}

 var a = add(20,30,10)// 20+30+10 =60

IIFE - Immediately Invoked Functional Expression

IIFE functions are wraped and called immediately .These kind of functions are called only once.

(function(a,b,c) {

    

  return a+b+c

})(10,20,30) //60

INLINE FUNCTION

   When we declare a function inside a function we can’t call that inside function alone in program those kind of functions are called as inline function.

function x() {

    console.log("hi")

    function add(a,b){

    console.log(a+b)}

    add(4,6)

      

    }

In the above example we can't call the function add separately this is called as inline function

 

CALL BACK FUNCTION

When you are calling outside function inside any other function is called call back. Passing function into the function

EXAMPLE PROB FOR CALL BACK FUNCTION

Write 4 different functions add,sub,mul and div.And put all  function inside array

var operator = [add,sub,mul,div]; and then write a function maths

function maths(ind,arr)
{

val1 =5;

val2 = 10

(write code to call add,sub,mul,div)

}

SOLUTION   

https://day9-callback.netlify.app/

ARROW FUNCTION

var add = (a,b) => a+b;

add(1,2) //3

ARRAY METHODS YOUTUBE VIDEO