The Complete JavaScript Guide - Functions

Functions are one of the fundamental building blocks in JavaScript.

• With functions you can reuse code
• You can write code that can be used many times.
• You can use the same code with different arguments, to produce different results.

The basic syntax to create a function in JavaScript

function functionName(parameter1 , paramater2){

      //  function body

}        

Function Declarations

• Every function should begin with the keyword function followed by,
• A user-defined function name that should be unique,
• A list of parameters enclosed within parentheses and separated by commas,
• A list of statements composing the body of the function enclosed within curly braces {}.

Basic declaration of a function in javascript

function calAddition(num1 , num2){

   return num1 + num2;
}
console.log(calAddition(6,4));


// output --- > 10        

Function Expression

• Function expressions can be stored in a variable assignment.?

Code for Function Expression

let calSub = function (x, y) {
	let z = x - y;
	return z;
}

console.log("Subtraction : " + calSub(7, 4));



// output ----> 3        

Arrow Function

• It is one of the most used and efficient methods to create a function in JavaScript

const name = () => { 
	console.log( "Hi I am Ajay!" ); 
} 

name();
        

Function Parameters

• The parameters are passed to the function within parentheses after the function name and separated by commas.
• A function in JavaScript can have any number of parameters and also at the same time
• a function in JavaScript can not have a single parameter.

function multiply(a, b) {
	b = typeof b !== "undefined" ? b : 1;
	return a * b;
}

console.log(multiply(69)); 


//output---->  69