Function in JavaScript

Introduction

 
All of us know that a function is a collection of statements executed when it is called at some point in a program. A function performs a specific task within a program independent of the other code in the program. We can call the function from anywhere within a program. We can also define the parameters to be passed to the function when the function is called. The parameters in a function are used to exchange information between a calling statement and the function. We can define a function by using the function keyword. 
 
Syntax for a function
 
Function1.jpg
 
The above syntax has the name of the function and the parameters of the function.
 
JavaScript functions are divided into two categories:
 
Function2.jpg
 

Function without Parameters

 
It does not contain parameters. The code in these functions is static, implying that the values of the members of these functions cannot be changed at runtime.
 

Function with parameters

 
It contains parameters in the parenthesis, such as integer and string. Unlike functions without parameters, the values of members of these functions can be changed at run time by passing different values of their parameters.
 
Now let's understand JavaScript functions using a simple example:
 
Function3.jpg
 
We have created a function named simple under the head section.
 
The simple() function shows an alert message with "Thank you".
 
The onload event handler under the BODY element calls the simple() function when the document is loaded in the browser.
 
Output
 
Function4.jpg


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