Functions in Javascript is a block of code that will get executed specifically when it gets a call.

Moreover, the function acts like a VIP which will only come on invitation other it will never get invoked until gets called.

There are various uses of using the function in javascript. Firstly, we don't have to write the same code again. Hence, it promotes the DRY principle (Don't Repeat Yourself).

The syntax of the function in Javascript is mentioned below -

function function_name(parameter1, parameter2, ..) { //Code to be executed }

The name of the `function` can be named with letters, digits, underscore, and dollar signs. There can be multiple `parameters` can be included in the function.

When Function Invokes?

The function gets invoked in some of the cases mentioned below -

• When a User clicks a button a function gets invoked.
• It gets called in the code itself.
• It is also self-invoked.

When encounters the `return` keyword in the code, the function will stop its execution as mentioned in the code below-

function multiply(a,b) { return a*b } let x = multiply(4,4) console.log(x)
//Output: 16

Function Expression

The Function Expression is the same as the Function Declaration. However, the main difference between the two is the function name.

The Function Keyword can be used with the function inside the parameter as mentioned in the code below -

const sqr_area = function(side) { return side * side; } console.log(sqr_area(2,3)); //Output: 6

Arrow Functions

The Arrow Functions is used to write the code more shortly and smartly. Arrow Functions was introduced in EC6.

The code showing the working of the Arrow Functions is mentioned below -

const sqr_area = (num) => { console.log(num*num); } //Call the function sqr_area(5); //Output: 25

##Regular Functions The regular functions are the simple functions which can be written as -

function multiply(a,b) { return a+b; }