JavaScript SyntaxError: Unterminated string literal

This JavaScript error unterminated string literal occurs if there is a string that is not terminated properly. String literals must be enclosed by single (') or double (") quotes.

Message:

SyntaxError: Unterminated string constant (Edge)
SyntaxError: unterminated string literal (Firefox)

Error Type:

SyntaxError

What happened?

There is a string in the code which is not terminated. String literals need to be enclosed by single (') or double (") quotes. JavaScript sees no difference between single-quoted strings and double-quoted strings.

Case 1: Missing Closing Quote

Error Cause:

If you start a string with a quote but forget to close it with another matching quote, you'll get an "Unterminated string literal" error.

Example:

let greeting = "Hello, World;
console.log(greeting);

Output:

SyntaxError: Unterminated string literal

Resolution:

Ensure that all string literals are properly enclosed with matching quotes.

let greeting = "Hello, World";
console.log(greeting);

Hello, World

Case 2: Unescaped Quote Inside a String

Error Cause:

If you use quotes inside a string without escaping them, it may cause the interpreter to mistakenly think the string has ended.

Example:

let message = "He said, "Hello!";
console.log(message);

Output:

SyntaxError: Unterminated string literal

Resolution:

Escape the internal quotes or use a different type of quote to enclose the string.

let message = "He said, \"Hello!\"";
console.log(message);

He said, "Hello!"

Case 3: Improper Use of Template Literals

Error Cause:

If using template literals (enclosed by backticks) but forget to close them, you will encounter an unterminated string literal error.

Example:

let template = `This is a template literal;
console.log(template);

Output:

SyntaxError: Unterminated string literal

Resolution:

Ensure that all template literals are properly closed with backticks.

let template = `This is a template literal`;
console.log(template);

This is a template literal