JS Validator
Validate your JavaScript code with detailed error reporting. Get instant feedback on syntax errors with line and column numbers.
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Paste your JavaScript and start typing to validate.
How JavaScript Validation Works
This validator parses your JavaScript using the Babel parser, which builds an abstract syntax tree (AST) from the input. If parsing succeeds, the code is syntactically valid. If it fails, the parser reports the exact location of the first error it encounters.
Validation checks syntax only - it does not execute the code or verify that variables, functions, or modules actually exist. It confirms that the code follows the grammar rules of modern JavaScript.
Common JavaScript Errors Detected
- Unexpected tokens - missing commas, brackets, or operators that break the parser.
- Unclosed brackets - missing closing
},), or]. - Unclosed strings - missing closing quotes on string literals or template literals.
- Invalid assignments - assigning to non-assignable expressions like function calls.
- Duplicate parameters - function parameters with the same name in non-sloppy mode.
Validation vs. Execution
This tool validates syntax, not runtime behaviour. Code can be syntactically valid but still throw errors at runtime due to undefined variables, type mismatches, or logic errors. Syntax validation catches errors before you run the code, saving time during development.