How to fix SyntaxError: Unexpected token in Node.js

The error message includes a line number where the parser failed. Check that line and the few lines before it.

The actual problem is often 1-5 lines before the reported error line. The parser only realizes there's a problem when it encounters the unexpected token.

Common examples:

Missing closing brace (error reported on line 5, problem on line 2):

function getData() {
  const data = fetchData();
  // Missing closing brace here

  console.log(data); // <- Error reported here

Unclosed string (error reported on line 3):

const message = "Hello World; // <- Missing closing quote
const name = "John
console.log(message); // <- Error reported here

Extra bracket:

const arr = [1, 2, 3];]  // <- Extra bracket here
console.log(arr); // <- Error reported here

Linters like ESLint can pinpoint syntax errors more clearly than runtime errors.

Install ESLint:

npm install --save-dev eslint
npx eslint init  # Follow the prompts to set up

Run ESLint on your file:

npx eslint your-file.js

ESLint output is typically more detailed:

file.js
  1:34  error  Parsing error: Unexpected token )

1 | function getData(a, b,) {
  |                         ^

This clearly shows there's an extra comma before the closing parenthesis.

In VS Code:
- Install the ESLint extension
- Problems will show directly in the editor with red squiggles
- Hover over the error for more details

Balance all brackets, parentheses, and braces.

Before (incorrect):

function getData() {
  const data = [1, 2, 3;  // <- Wrong bracket type
  return data
// Missing closing brace

After (correct):

function getData() {
  const data = [1, 2, 3];  // <- Correct bracket type
  return data;
}

Use an editor with bracket matching:
- Place cursor on an opening bracket and it highlights the closing one
- Most editors (VS Code, WebStorm, Sublime) support this
- Use keyboard shortcuts to jump between matching brackets

Common bracket pairs:
- ( ... ) - Function calls, grouping
- [ ... ] - Arrays, indexed access
- { ... } - Objects, blocks, statements

Ensure all string literals have matching quotes.

Before (incorrect):

const name = "John;
const city = 'New York;
const message = `Hello`;  // backticks don't match quotes above

After (correct):

const name = "John";
const city = 'New York';
const message = `Hello`;

Important: Match quote types:

"string with double quotes"   // Correct
'string with single quotes'   // Correct
`string with backticks`     // Correct
"mismatched quote'            // WRONG

Check for smart quotes:
If you copied code from a website, Word document, or PDF, it may contain "smart quotes" instead of regular quotes.

Wrong (from Word/PDF):

const message = "Hello";  // These are fancy curly quotes

Right (plain text):

const message = "Hello";  // These are straight quotes

Fix: Delete the string and retype it manually in your editor, or paste into a plain text editor first.

Remove invisible or invalid characters, especially from pasted code.

Check for invisible characters:

# Show all whitespace characters (including invisible ones)
cat -A your-file.js | head -20

# Look for unusual characters like zero-width spaces, special unicode
hexdump -C your-file.js | head -20

Common culprits when pasting:
- Smart quotes from Word: curly quotes (replace with regular straight quotes)
- Zero-width spaces (from some web interfaces)
- Em dashes and en dashes (replace with -)
- Tab characters mixed with spaces

Solutions:
1. Delete the problematic line and retype manually
2. Paste into a plain text editor first (Notepad, plain text mode)
3. Use your editor's find-and-replace to swap smart quotes with regular quotes

Using sed to clean common issues:

# Replace smart quotes with regular quotes
sed -i 's/[""]/"/g; s/['']/'"'"'/g' your-file.js

Do not use JavaScript reserved words as variable or function names.

Reserved words you cannot use:

// Cannot use as names:
const if = 5;        // WRONG
const class = {};    // WRONG
function for() {}    // WRONG
let while = true;    // WRONG

Legal alternatives:

// Correct versions:
const ifCondition = 5;
const myClass = {};
function loop() {}
let whileActive = true;

Complete list of reserved words:
Abstract, arguments, await, boolean, break, byte, case, catch, char, class, const, continue, debugger, default, delete, do, double, else, enum, eval, export, extends, false, final, finally, float, for, function, goto, if, implements, import, in, instanceof, int, interface, let, long, native, new, null, package, private, protected, public, return, short, static, super, switch, synchronized, this, throw, throws, transient, true, try, typeof, var, void, volatile, while, with, yield

Context matters: Some reserved words can be used in specific contexts (like as object properties):

const obj = {
  class: 'main',  // OK as object property
  for: function() {},  // OK as object property
};

console.log(obj.class);

If parsing JSON, ensure the data is actually valid JSON, not HTML or malformed data.

Common issue - server returns HTML instead of JSON:

// If your server returns an error page as HTML
const response = await fetch('/api/data');
const json = await response.json();  // <- Error if response is HTML

Fix - check content type first:

const response = await fetch('/api/data');

if (!response.ok) {
  throw new Error(`HTTP ${response.status}`);
}

if (!response.headers.get('content-type')?.includes('application/json')) {
  throw new Error('Response is not JSON');
}

const json = await response.json();

Validate JSON structure:

// Valid JSON
{
  "name": "John",
  "age": 30,
  "items": [1, 2, 3]
}

// INVALID JSON - trailing comma
{
  "name": "John",
  "age": 30,  // <- Extra comma not allowed
}

// INVALID JSON - single quotes
{
  'name': 'John'  // <- Single quotes not valid in JSON
}

// INVALID JSON - unquoted keys
{
  name: "John"  // <- Keys must be quoted in JSON
}

Test JSON validity:

# Use jq to validate JSON
echo '{"name":"John"}' | jq .

# Pretty-print and validate
curl https://api.example.com/data | jq .