Functions in javascript.

Functions are used to execute any task that repeats itself.

//Declare Function
function singHppyB(){
    console.log("Happy Birthday!")
}

// Call Function
singHppyB();

//Storing return value in new variable and calling it
function twoPlus(){
    return 2+5;
}
twoPlus();

const returenedValue=twoPlus();
console.log(returenedValue);

Function with parameters.

Function parameters are the names listed in the function definition.

Function arguments are the real values passed to (and received by) the function.

    // adding parameters
    function sum(num1,num2){
        return num1+num2;
    }

//arguments passed
    const returnV=sum(3,5);
    console.log(returnV);

Function Expression.

Storing the function in the variable.

//const ,let , var ; anything can be used for declaration 
const happy=function(){
    console.log("BJKs hxdjK")
}

happy();

Arrow Functions.

const name=(num1,num2,num3)=>{
   return num1+num2+num3 
}

const numbers=name(2,3,4);
console.log(numbers);

Another way to represent Arrow Function.

//it means a variable named "Number" takes "num" as parameter and returns num%2===0
const Number= num => num % 2 === 0;
console.log(Number(20));

Hoisting.

Hoisting means "calling of a function or variable "before declaring it. However, we can do it with variable declaration or function, not with function expression.

hello();

function hello(){
    console.log("hello");
}

//function expression(it will not give output through this.)
const hello = function(){
    console.log("helloo");
}

Nested Functions.

function app(){
    const myfunc=()=>{
        console.log("Hey");
    }

    const add=(num1,num2)=>{
        return num1+num2;
    }

    console.log("inside app");
    myfunc();
}
app();

Lexical Scope.

Lexical scope is the set of rules for how the JavaScript engine finds variables and functions when executing code, relative to where you've defined them at author-time.

//here myVar is found using lexical scope.
const myVar="VALUE1"
function myApp(){
function myFunc(){
    const myFunc2 =()=>{
        console.log("Inside loop",myVar);
    }
    myFunc2();
}

console.log(myVar);
myFunc();
}

myApp();