JavaScript validator

One warning
One undefined variable
One unused variable

JavaScript Validator is intuitively designed to detect errors in JavaScript code, a scripting language. This tool saves programmers from hours of finding bugs in the JS code. 

There can be some syntax errors that must be fixed to ensure that the JS code runs smoothly. You can quickly improve the quality of your code when you know where the problem lies. 

No matter the runtime environment in which you need to execute your code, our JS validator lets you do it quickly. You can conveniently specify whether you want to check the effectiveness of your code in a browser, Jquery, CouchDB, or Node.js. 

You can also indicate if the JS code with bitwise operators, eval, statement, or expressions should be validated or flagged as an error. 

You can leverage our tool for free whenever you encounter a bug in your JavaScript code. Following your instructions, our advanced tool will take only a moment to analyze the JS code, providing you with a list of potential errors and warnings. You may ignore the warnings, but the detected errors, such as undefined or unused variables, must be resolved. 

How to Find JavaScript Errors? 

Following these steps, you can easily use our JS Validator to check errors in javascript syntax:

Step 1 - Enter JS Code 

Here are a few ways (any of which) you can follow to enter the "javascript code" for a quick syntax validation:

  • Upload a code file 
  • Copy-paste the code
  • Manually type the code
  • Fetch the code via the URL

Just make sure to enter the JS code without any omissions.

Step 2 - Specify Runtime Environment 

Select any of the following options to indicate in which "runtime environment" you want to validate the javascript code:

  • Browser
  • Jquery
  • CouchDB
  • Node.js

You can select multiple runtime environments at a time. 

Step 3 - Make Necessary Exceptions

Utilize the "tolerate" feature to highlight which of the following are acceptable or not during validation:

  • Bitwise operators
  • Eval
  • Statement
  • Expressions

You can make multiple exceptions at the same time. 

Step 4 - Check the Result

There's no need to click on any button to run our JS validator. It automatically processes the given code and validates it after entering it. 

Take into account that our javascript validator will enlist the following to help you validate your javascript code:

  • Warnings
  • Errors 

Even if you make changes to the JS code (while validating it), you'll get quick results without reloading our tool. 

Why Use Our JavaScript Validator? 

Javascriptvalidator.net is your go-to solution to identify unforeseen errors in JS code syntax. It is an advanced tool that works best to help you understand why your JavaScript code could be running more effectively. There can be various reasons you need to validate your code, such as identifying syntax errors, but whenever you need to do it, you must use a highly-functional tool, just like our JS validator. 

Let's find out what our JavaScript Validator offers you:

Improved Functionality

JavaScript code validation becomes hassle-free with our advanced JS code checker. It scans JavaScript syntax for common bugs, ensuring you can easily find out why your code is not working correctly. It flags both errors and warnings, which must be looked into. For instance, if there are any undefined values, implicit type conversion, or wrong logic, it will alert you.

Advanced Features 

Thanks to our tool's multiple intuitive features, you can easily customize the settings and specify how you would like to validate your JS code. For instance, you can highlight which runtime browser your code should be checked for errors and warnings. You can also make some exceptions, such as instructing the tool not to flag bitwise operators or Eva as errors. 

Quick Results 

There's no need to wait for minutes when our JS validator takes only a second to run your code and check it for potential errors. Just as you enter the code, it automatically displays the results. It doesn't even require you to reload the page. You can easily edit or replace the code. Moreover, it will take only a single click if you want to fetch JS code directly from a URL and scan it for errors. 

Free Access 

Free unlimited access for a lifetime. That's what you get when you use our JS validator. We want nothing more than the ease of programmers, so we make sure that they don't have to pay to validate their JS syntax. No matter how many times you use it, you will not need to sign up or get a subscription plan. All features and functions are accessible for free.

Understanding JavaScript 

JavaScript is a free scripting language that works on both the server and client sides. It is text-based and works with HTML and CSS to enhance code functionality and add interactive elements. In short, JS breathes life into static sites and makes them interactive. 

Most websites use JavaScript, and all modern web browsers support it without plugins. With a large community and a rapidly evolving ecosystem, it has a large user base. Indeed, a web developer today must be familiar with JavaScript to work on a web project. 

What is JavaScript?

A JavaScript scripting language is a cross-platform, object-oriented scripting language used for creating dynamic web pages with elements such as animated graphics, clickable buttons, and pop-up menus. Undoubtedly, it is one of the best web browser technologies available today. The JavaScript scripting language is used to create and control dynamic website content, such as anything on your screen that moves, refreshes, or otherwise changes, without requiring you to reload it. Some features of JavaScript are given below:

  • animated graphics
  • photo slideshows
  • autocomplete text suggestions
  • interactive forms

Creating new applications using server-side JavaScript versions and frameworks, such as Node.js, is also possible. The JavaScript frameworks offer performance benefits as well as ready-to-use solutions.

For example, a web browser window or webpage can be programmed to control objects in its environment using JavaScript. 

JavaScript includes a standard library of objects, such as Array, Date, and Math, as well as a basic set of language components, such as operators, control structures, and statements. Extending Core JavaScript with additional objects can be used for various applications, such as Client-side and Server-side JavaScript.

Client-side JavaScript provides objects for controlling the browser's Document Object Model (DOM). For example, client-side JavaScript enables a program to add HTML elements to an HTML file and respond to user actions such as mouse clicks, form entries, and page navigation.

Server-side JavaScript extends the basic language by providing the objects needed for server-side JavaScript. For example, it facilitates the creation of connections between applications and databases or supports file I/O operations. 

JavaScript Syntax

// JavaScript Document

$(document).ready(function(){   $('.owl-carousel').owlCarousel({     loop: true,     margin: 20,     responsiveClass: true, nav: false, dots: true,     autoplay: true,     responsive: {         0:{             items:1,         },         600:{             items:3,         },         1000:{             items:4,         }     }   }); $('.menu-toggle').click(function(){ $('.main-menu').fadeToggle() }); });

What is JavaScript Used For?

As JavaScript is one of the most widely used and dynamic programming languages today, it creates rich web experiences for PCs, tablets, and mobile devices. Undoubtedly, it is a world-class language with a thriving development environment and a committed community committed to its continuous development.

JavaScript is used for a variety of purposes. Following are some of its uses:

  • Adding interactivity to websites—To make your website more than a static page of text, you will have to use JavaScripting.
  • Developing mobile applications — JavaScript is not just for websites... it's also used to create apps for smartphones and tablets.
  • Creating web browser-based games — Have you ever played a game directly from your web browser? It is probably because of JavaScript.
  • Back-end web development: JavaScript is most commonly used on a website's front end, but it is also a versatile enough scripting language to be used on the back-end infrastructure.

What are the Main Features of JavaScript?

Understanding the main features of JavaScript is essential to understanding the language properly. We have discussed the five features of JavaScript in the following.


JavaScript is a lightweight scripting language designed primarily for handling data in browsers. Additionally, JavaScript Code is lightweight and is intended primarily for client-side execution, such as web applications. Because it is not a general-purpose language, it has limited libraries. 

Dynamic Typing

The JavaScript programming language supports dynamic typing. The term dynamic typing refers to the fact that a variable's data type is only declared at runtime. In this way, programmers are not required to declare the type of variables while coding, simplifying the coding process and making it easier to implement.

Using JavaScript, we declare variables using the var, const, or let keywords before their names without specifying their data types.

Functional Style

It is important to note that JavaScript is a functional programming language, meaning that even objects are constructed using constructor functions, and each constructor function represents an individual object type. The JavaScript functions can also be used as objects and be passed on to other functions.

Platform Independent

JavaScript is platform-independent or portable, meaning you can write JavaScript code once and run it anywhere at any time. Generally, JavaScript programs can run on any platform or web browser without altering their output.

Object-Oriented Programming

The concept of OOP has been refined with ES6. In JavaScript, Code Reuse Patterns, or inheritance, are also essential elements of OOP. Although JavaScript developers rarely use this capability, it is available to all users. 

What are the Types of JavaScript Errors?

The errors must occur in any programming language. In JavaScript, the following six error constructors are most commonly used:

Syntax Error

This is one of the most common errors we encounter. It occurs when we attempt to type code that is not understood by the JS engine.


Typing pint in place of print

The JS engine catches an error like this during parsing. It is important to note that our code is put through various stages in the JS engine before we can see the results on our terminal.

Reference Error

Errors of this type occur when a variable reference cannot be found or declared.


const l=console.log

const cat = "cat"



Type Error

Typically, this error is caused by misusing a value outside the scope of its data type.


let number = 5;

console.log(number.split("")); //Converting a number to an array will throw an error


What is JavaScript used for?

Programmers use JavaScript to create interactive web pages, such as browsers' or applications' user interfaces. It works hand-in-hand with HTML and CSS to ensure that all web pages' interactive elements and functions can be used as required. 

Are JavaScript and HTML the same?

No. There's a difference between using JS and HTML. JavaScript is a "scripting language," whereas HTML is a "markup language." JavaScript must be loaded and run with HTML markup to make a web page interactive and usable. 

What is the general syntax of JavaScript?

The JavaScript code comprises a series of instructions known as statements. At the same time, the JS statements consist of values, expressions, operators, keywords, and comments. The JavaScript syntax can have some fixed values and variable values. 

What causes a JavaScript error?

There can be some omissions or typos in the syntax, which may lead to JavaScript errors. For instance, incorrect variable names, missing parentheses, and unmatched brackets can cause a JS error. The JavaScript code can not be executed if there are syntax errors. 

How to fix JavaScript errors?

You need to check for errors if your JS code is not running. You can use a JavaScript validator to identify bugs with ease. Once you know what type of error this is, you can quickly fix it. Check for cross-browser compatibility and other technical issues if it is not a syntax error.