JavaScript function- Complete guide 2022

In this article, we will be covering all functions in JS and how to use them in JavaScript. Before jumping directly to the functions in JS, we will learn about JavaScript and the basics of what exactly a function is in this context. So if you are new to all these concepts, don’t worry, we will be covering it right from the fundamentals and will then move to differences. So keep reading.

Introduction

JavaScript is one of the most used languages when it comes to building web applications as it allows developers to wrap HTML and CSS code in it to make web apps interactive. It enables the interaction of users with the web application. It is also used for making animations on websites and has a large community on GitHub. JavaScript has tons of libraries, one of which is React which we will be covering in this article later. 

Use cases: 

• Building web server and its interactive functions
• Animations and graphics, adding special effects to web components
• Validating forms and exception errors
• Adding behavior and functionalities to web pages

In JavaScript, promises are used to handle asynchronous operations. When dealing with several asynchronous activities, where callbacks might cause callback hell and unmanageable code, they are simple to manage.

JavaScript function

A function is a collection of statements that take inputs, do a certain calculation, and return results. A function is essentially a group of statements that executes a set of activities or performs a calculation and then returns the result to the user.

The goal is to group together some regularly or repeatedly performed actions and create a function so that we may call it instead of writing the same code over and over for different inputs.

JavaScript, like other programming languages, allows you to use functions. You’ve probably seen some of the most often used JavaScript functions, such as alert(), which is a built-in function in JavaScript. However, JavaScript also allows us to write user-defined functions.

The keyword function can be used to build functions in JavaScript. The basic syntax for writing a JavaScript function is illustrated below.

Syntax:

function functionName(Parameter1, Parameter2, ..)
{
    // Function body
}
Code language: JavaScript (javascript)

In JavaScript, we must first use the keyword function, followed by the name of the function and parameters enclosed in parenthesis. The body of the function is the section of the function that is inside the curly braces.

Definition of a function

We must first develop a user-defined function in JavaScript before using it. In JavaScript, we can use the aforementioned syntax to build a function. A function definition is often referred to as a function declaration or statement.

The following are the guidelines for writing a JavaScript function:

Every function should begin with the keyword function, followed by, and finally, and finally, and finally, and finally, and finally, and finally

The name of a user-defined function must be unique.

A list of parameters separated by commas and contained in parenthesis.

Curly braces encompass a list of statements that make up the function’s body. {}

function calcAddition(number1, number2)
{
	return number1 + number2;
}
Code language: JavaScript (javascript)

In the preceding example, we constructed a function called calcAddition, which takes two numbers as parameters and returns the sum of the two numbers.

Parameters of the function

We’ve heard a lot about function parameters so far, but we haven’t gone over them in-depth. Parameters are extra pieces of data provided to a function. The function calcAddition, for example, is used to calculate the addition of two numbers in the example above. This function is supplied the two numbers on which we wish to conduct the addition operation as inputs. The parameters are separated by commas and supplied to the function within parentheses after the function name. A JavaScript function can have any number of parameters while also being unable to have a single parameter.

Calling Functions

After you’ve defined a function, you’ll need to call it in order to use it. A function can be called by using the name followed by the argument values contained in parenthesis and a semicolon at the end. The following syntax demonstrates how to use JavaScript to call functions:

functionName( Value1, Value2, ..);

The following is an example program that demonstrates how functions in JavaScript work:

<script type = "text/javascript">

// Function definition
function welcomeMsg(name) {
document.write("Hello " + name + " welcome to Codedamn");
}

// creating a variable
let nameVal = "Admin";

// calling the function
welcomeMsg(nameVal);

</script>
Code language: JavaScript (javascript)

Return Statement

There are times when we want a function to return some values after it has performed some actions. In such circumstances, the return statement in JavaScript might be used. This is an optional statement that is usually placed at the end of a JavaScript function. Take a look at our first example, which uses the calcAddition function. This function adds two numbers together and returns the result. The return statement’s most basic syntax is as follows:

return value;

The return statement starts with the keyword return, followed by the value we want to return. Instead of returning the value directly, we can use an expression.

Conclusion

This was all about the functions in JavaScript. If you have any query related to React or JavaScript, do drop it down in the comment section also do check out codedamn courses if you want to learn more about JavaScript and React with its use cases and amazing projects. They also have an in-built playground for different programming languages and environment sets so do check that out and join codedamn’s community! 

Hope you like it.