Invalid JavaScript syntax that prevents the script from parsing.
A SyntaxError is thrown when the JavaScript engine encounters code that violates the language's grammar rules. This happens before any code runs — the engine parses the entire script first, and if parsing fails, nothing executes.
Causes include: missing or extra brackets/braces/parentheses, using reserved words incorrectly, missing commas in object literals or function arguments, bad JSON syntax, or copy-pasting code from different environments with invisible characters.
1const user = {2 name: "Alice"3 age: 30, // Missing comma after "Alice"4 role: "admin"5};6 7console.log(user.name);1const user = {2 name: "Alice", // Fixed: added comma3 age: 30,4 role: "admin"5};6 7console.log(user.name); // "Alice"Simulate standard system builds to trigger compiler trace records and track memory crashes locally.
On line 2, the `name` property's value `"Alice"` is not followed by a comma before the next property `age`. JavaScript's object literal syntax requires a comma between properties. The parser sees `age` as an unexpected token and throws a `SyntaxError`.