Check JavaScript Syntax & Find Errors Instantly (ES2024 Support)
Check JavaScript code for syntax errors instantly in your browser. Get exact line and column numbers for each error, plus code statistics like function count, variable declarations, and imports. Free and works offline.
How to Use JavaScript Syntax Checker
How to Use the JavaScript Syntax Checker:
Paste Your Code: Type or paste your JavaScript into the editor. The panel shows line numbers on the left for easy reference.
Click "Check Syntax": Click the blue "Check Syntax" button to validate your code. A green banner confirms no errors; a red banner shows the exact line and column of the error.
Read the Error: The Error panel shows the exact line number, column, and a description such as "Unexpected token" or "Unexpected end of input". The error line is highlighted in red in the line number gutter.
Fix and Re-check: Fix the reported error and click "Check Syntax" again. Only the first syntax error is shown per check.
Review Statistics: After checking, the Statistics panel shows line count, function/arrow count, variable declarations (var/let/const), import statements, and comment count.
Use Examples: Click the example buttons to load valid and invalid JavaScript snippets and see how the checker works.
Supported syntax:
- ES2024 including optional chaining, nullish coalescing, logical assignment
- Async/await and top-level await (ES modules)
- Classes with private fields (#field)
- import/export statements
- Template literals, destructuring, spread/rest
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