JavaScript for beginners - Chapter 21 - Function (Methods) in JavaScript

Javascript Function(Method)
Function in JavaScript.
A function is a block of reusable code.
Advantage of using a function :
A function allow us to write code once and use it many times as we want just by calling the function.
JavaScript function syntax :
function functionName(parameter1, parameter2,...parameter_n)
{
//function statements
}

Use the function keyword to define a function, followed by the name of the function .
The name of the function should be followed by parentheses.
Function parameters are optional.
Example : Function to add two numbers

function mutliplyNumbers(firstNumber, secondNumber)
{
var result = firstNumber * secondNumber;
return result;
}

Calling the JavaScript function :
Call the JavaScript function by specifying the name of the function and values for the parameters if any.

function mutliplyNumbers(firstNumber, secondNumber)
{
var result = firstNumber * secondNumber;
return result;
}

var multiply = mutliplyNumbers(5, 5);

The parameters that are missing values are set to undefined.
When we specify too many parameter values to the calling function, the extra parameter values will be ignored.
It’s not compulsory, that JavaScript function should always return a value. It totally depends on what you want the function to do.
If an explicit return is omitted, undefined is returned automatically.

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