SyntaxError: Unexpected token
Error message
Unexpected token 'x'
Quick summary
JavaScript found a symbol where it shouldn't be — usually a missing bracket, comma, or quote earlier in the code.
Why this happens
Missing comma between items in an array or object literal
Unclosed string, parenthesis, or bracket from a previous line
Extra punctuation or a stray character in the code
Minimal example
const arr = [1, 2 3];const arr = [1, 2, 3];A comma is missing between 2 and 3 — the parser sees 3 where it expected a comma or closing bracket.
How to diagnose
Look at the token mentioned in the error and the line before it
Check for missing commas, brackets, or quotes near the reported location
Use a linter or formatter to highlight the syntax issue
How to fix
Add the missing comma, bracket, or quote
Remove any extra or stray punctuation
Run the code through a formatter (Prettier) to spot structural issues
How to prevent
Use a linter (ESLint) to catch syntax errors as you type
Enable editor syntax highlighting and bracket matching
Related Resources
Related Glossary
Related Lessons
- JavaScript Overview
Learn JavaScript fundamentals
Related Practice
- Find the Arrow Function Error
Practice spotting syntax errors in functions.
Related Tools
- JSON Formatter
Format and validate JSON to catch syntax errors.
- JSON Validator
Validate JSON syntax to find unexpected tokens.