JavaScript Validator

JavaScript Validator – Check JS Syntax Online

The JavaScript validator (JS validator) checks whether your code is syntactically valid JavaScript. If it is not, you get the exact line and column of the error and a code frame with a caret pointing to the problem — much faster than reading a minified browser error.

How it works

Your code is parsed with Acorn, the small, standards-compliant JavaScript parser used inside webpack, Rollup, and many other tools. Acorn follows the latest ECMAScript specification, so modern syntax such as optional chaining, class fields, private methods, top-level await, and import/export is recognized.

Options

• Code type – ES module allows import/export and top-level await and applies strict-mode rules. Classic script is for code loaded with a regular <script> tag, where those statements are not allowed.
• Allow JSX – accept React-style JSX elements.

The report

For valid code, the report confirms there are no syntax errors and lists simple statistics: lines, top-level statements, functions, classes, imports, and exports. For invalid code, it shows the error message, the position, and a code frame:

> 3 |   if (name.length > 10 {
    |                        ^

Common syntax errors

• A missing closing parenthesis, bracket, or brace.
• A trailing operator (a +) or a missing comma between object properties.
• Using await outside an async function in a classic script.
• Reserved words such as class or enum used as variable names.
• Strict-mode violations in modules, such as duplicate parameter names or with statements.

What it does not check

This is a syntax check. It does not run your code, find undefined variables, or enforce style rules — use ESLint for linting and TypeScript for type checking.

Related tools

Format valid code with the JavaScript Beautifier, minify it with the JS Minifier, and check your stylesheets with the CSS Validator.