JavaScript Functions

JavaScript Functions

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Updated on Dec 27, 2023 15:01 IST

A JavaScript function is a block of reusable code designed to perform a particular task, enhancing code efficiency and organization. Functions are invoked or called to execute their defined operations and can accept parameters and return values, allowing for flexible and dynamic programming.

You can invoke a function anywhere in your code, which is a collection of reusable code. This avoids the need to write the same code repeatedly. Programmers can use it to write modular codes. Using functions, a programmer can break up a large program into several smaller, more manageable components. A section of code called a JavaScript function is created to carry out a particular task. When “something” invokes a JavaScript function, it begins to run. This article will discuss JavaScript functions and how to use them. 

Table of contents

JavaScript Functions

The features required to construct blocks of code using functions are supported by JavaScript, just like any other smart programming language. Although we frequently used them, these functions had only ever been defined once in the core of JavaScript.

We can also create our functions in JavaScript. The following section covers how to create custom JavaScript functions. The main advantages or functions of JavaScript are

  • Reusability of Code: By repeatedly calling a function, we can reduce the amount of coding required.
  • Less coding: This results in more compact software. To complete a routine activity, we don’t need to write much code each time.

Syntax of JavaScript Function

function functionName([x1, x2, …xN]){  

 //code for execution  

}  

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JavaScript Function Parameters

We have only seen functions with no parameters up to this point. But when invoking a function, it is possible to pass several parameters. These passed arguments can be recorded within the function and subjected to any manipulation. Multiple parameters can be passed to a function, separated by commas.

JavaScript Return Statement

A return statement is an optional part of JavaScript functions. You must do this if the user wishes to have a function return a value. The last sentence in a function should be this one.

For instance, if you pass two numbers into a function, you can anticipate the function to return the result of multiplying the two values in the calling program.

Let us see the JavaScript code below and understand the basics of functions:


 
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript Functions</h2>
<p>The demo calls a function that performs a specific calculation, returning the output:</p>
<p id="demo"></p>
<script>
function myF(x1, x2) {
return x1 * x2
}
document.getElementById("demo")[removed] = myFunction(5 3);
</script>
</body>
</html>
Copy code

Output:

JavaScript Functions

The demo calls a function that performs a specific calculation, returning the output:

15

Read: Access Modifiers in Java

Also, Read: Data Types in Java – Primitive and Non-Primitive Data Types Explained

JavaScript Function Object

The function constructor’s job in JavaScript is to build a new Function object. The code is run on a global scale. Directly calling the function () results in a dynamic, insecure function creation.

JavaScript Function Methods

Method  Description
apply() It is used to invoke a function that takes this value as well as one parameter in an array.
call() It has a list of arguments and this value and is used to call a function.
bind() It is used to develop new functionality.
toString() It gives back the outcome as a string.

Read: Interfaces in Java

Example:


 
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript Functions</h2>
<p>The demo calls a function that performs a specific calculation, returning the output:</p>
<p id="demo"></p>
<script>
function myF(x1, x2) {
return x1 * x2
}
document.getElementById("demo")[removed] = myFunction(5 3);
</script>
</body>
</html>
Copy code

Output

125

Conclusion

In this article, we have understood the following points:

  • Declare a function by using the function keyword.
  • To invoke a function, use the functionName() method.
  • If a function doesn’t explicitly return a value, it will always implicitly return undefined.
  • To explicitly return a value from a function, use the return statement.
  • Function parameters are stored in the arguments variable, an object with array-like properties inside a function.
  • Using the hoisting technique, you can call a function before defining it.

Contributed by Megha Chadha

Top FAQs on JavaScript Functions

What is a JavaScript function?

A JavaScript function is a block of code designed to perform a specific task. It can be called (invoked) from other parts of the code, and it helps in organizing and reusing code effectively.

How do you declare a function in JavaScript?

A function is declared using the function keyword, followed by a name, parentheses () containing any parameters, and curly braces {} enclosing the function's code block. For example: function myFunction() { /* code */ }.

What is the difference between function parameters and arguments?

Parameters are variables listed as part of the function's definition. Arguments are the actual values passed to the function when it is invoked.

How do you call or invoke a function in JavaScript?

A function is called by writing the function name followed by parentheses. If the function requires arguments, they are placed inside the parentheses. For example: myFunction(arg1, arg2).

What is an anonymous function in JavaScript?

An anonymous function is a function without a name. They are often used as arguments to other functions or as immediately invoked function expressions (IIFEs).

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