Functions in JavaScript

What is a Function?

• A function is a block of code or a subprogram designed to perform a particular task.
• Function is executed only when it is called. This is called invoking/calling a function. Thus it eliminates writing the same code again and again.
• Values can be passed into functions and used within the function body.

Function always returns a value, if no return type is specified, the function will return undefined .

JavaScript Function Syntax

function (parameter1, parameter2, parameter3,….) {
  // code to be executed
}

JavaScript supports 4 types of function invoking:

1. Function having no arguments and no return value
2. Function having arguments and no return value
3. Function having return value and argument(s)
4. Function having return value but no arguments

Function having no arguments and no return value

In JavaScript, if there’s no specified return type, the function will return undefined. Consider the following example:

R

Result

Within myFunction!

Function having arguments and no return value

Consider the following example:

    
     // Function is called

Result

5

Here the ‘return’ statement is missing. But arguments are passed to the function and used in the block of code.

Function having return value and arguments

Result

5

Function having return value but no arguments

Result

myFunction