Browser tool Runs locally
JavaScript Validator
Validate JavaScript syntax in your browser. Precise parser errors with line and column locations, no code execution, no upload.
JavaScript input
0 chars⌘/Ctrl + Enter to validate
Validation report
Click Validate JavaScript to check the input.
Examples:
What this validator checks
- Syntax - whether the source is valid JavaScript.
- Location - line and column where the parser stopped.
- Unsupported syntax - a clear message for JSX, TypeScript, or other extensions.
How to validate JavaScript
- Paste JavaScript in the input panel.
- Click Validate JavaScript.
- Review the report.
JavaScript syntax errors explained
A syntax error means the parser could not make sense of the source at a specific position.
Common JavaScript mistakes
- Unbalanced braces or parentheses.
- Missing commas in object literals, array literals, or function argument lists.
- Unterminated strings and template literals.
- Reserved words as identifiers.
- Unsupported syntax (JSX, TypeScript).
- Top-level await in script mode.
JavaScript Validator vs. JavaScript Formatter
A formatter makes source readable. A validator reads the source and reports whether it is syntactically valid.
Frequently asked questions
- What does this JavaScript Validator check?
- It checks JavaScript syntax using the same ECMAScript parser the Formatter uses.
- Does it execute my code?
- No. The parser reads source as text; nothing is evaluated.
- Is my JavaScript uploaded?
- No. Parsing and validation run entirely in your browser.
- Does it support TypeScript or JSX?
- No. Non-standard syntax is reported clearly.
- Is this the same as ESLint?
- No. ESLint is a linter; this tool is a syntax checker.