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How to Solve the "SyntaxError: missing ) after argument list" in JavaScript

The SyntaxError: missing ) after argument list is a common syntax error in JavaScript. It occurs when the JavaScript engine is trying to parse the arguments of a function call but encounters a syntax that it doesn't understand. While the message mentions a missing parenthesis ), the root cause is almost always a different syntax mistake within the argument list.

This guide will explain the common mistakes that trigger this error and show you how to fix them.

The Core Problem: Invalid Syntax in a Function's Argument List​

This error is thrown by the JavaScript parser when it is reading the code inside a function call's parentheses (). It expects a comma-separated list of expressions (arguments). When it finds two arguments next to each other without a comma or a valid operator between them, it gets confused and reports a syntax error.

Cause 1 (Most Common): Missing Comma Between Arguments​

This is the most frequent cause of the error. You intend to pass multiple arguments to a function but forget to separate them with a comma.

Example of problem:

// Problem: Two arguments are next to each other without a separator.
function sum(a, b) {
  return a + b;
}

sum(10 15); // ⛔️ SyntaxError: missing ) after argument list
note

The parser sees 10 and then 15 and doesn't know what to do, as it was expecting a comma or a closing parenthesis.

Solution: Always separate arguments in a function call with a comma.

// ✅ Correct: Arguments are separated by a comma.
function sum(a, b) {
  return a + b;
}

sum(10, 15); // Returns 25

Cause 2: Incorrect String Concatenation​

This often happens when you try to join two string literals or a string and a variable without using the + operator.

Example of problem:

// Problem: Two string literals without the `+` operator.
console.log('Hello' 'World'); // ⛔️ SyntaxError

const name = 'Alice';
console.log('Welcome, ' name); // ⛔️ SyntaxError

Solution: use the addition (+) operator to concatenate strings or use a template literal.

// ✅ Correct: Using the `+` operator
console.log('Hello' + 'World');

const name = 'Alice';
console.log('Welcome, ' + name);

// ✅ Correct (Modern): Using a template literal
console.log(`Welcome, ${name}`);

Cause 3: Using Template Literal Syntax in a Regular String​

Template literals (${...}) are a special feature that only works inside strings delimited by backticks (`). Using this syntax in a regular single or double-quoted string will cause a syntax error.

Example of problem:

// Problem: Using `${...}` inside a single-quoted string.
const data = 'some data';
console.log('Metadata: ${data}'); // ⛔️ SyntaxError

Solution: ensure you are using backticks for template literals.

// ✅ Correct: Using backticks for the template literal.
const data = 'some data';
console.log(`Metadata: ${data}`); // Output: "Metadata: some data"

Cause 4: A Missing Closing Parenthesis​

While less common, the error message can be literal. If you have a complex, nested function call, you might simply forget a closing parenthesis.

Example of problem:

// Problem: The outer console.log is missing its closing parenthesis.
console.log("The result is:", sum(10, 5) // ⛔️ SyntaxError

Solution: carefully check your parentheses to ensure that every opening ( has a corresponding closing ). Your code editor's bracket highlighting can be very helpful for this.

// ✅ Correct: All parentheses are balanced.
console.log("The result is:", sum(10, 5));

Conclusion​

The SyntaxError: missing ) after argument list is almost always a signal that you have made a simple syntax mistake inside a function call.

To fix it, check for these common issues:

  • Missing commas between multiple arguments.
  • Missing + operators between strings you are trying to concatenate.
  • Incorrect use of ${...} in a string that is not a template literal (i.e., not using backticks `).
  • A genuinely missing closing parenthesis ) in a complex expression.

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