TS1214: Identifier expected. '{0}' is a reserved word in strict mode. Modules are automatically in strict mode

TypeScript is a statically typed superset of JavaScript that provides developers with a powerful way to write robust and maintainable code. In TypeScript, you can define types, interfaces, enums, and more, which help in catching errors during development rather than at runtime. Types (which represent different data formats), play a crucial role in TypeScript as they help enforce the structure and behavior of the data your application works with. If you're looking to learn more about TypeScript or utilize AI tools like gpteach to enhance your coding skills, consider subscribing or following our blog!

Important: What is a Superset Language?

A superset language is one that extends the capabilities of another programming language. TypeScript, for instance, is a superset of JavaScript, meaning every valid JavaScript code is also valid TypeScript code, but TypeScript adds additional features and types that JavaScript does not have.

The Error: TS1214

The error message TS1214: Identifier expected. '{0}' is a reserved word in strict mode. Modules are automatically in strict mode. can be daunting, especially if you are new to TypeScript. This error occurs when TypeScript encounters a reserved word (like class, function, etc.) where it expects an identifier (names you give to variables, functions, etc.).

Example of the Error

let class = "myClass"; // Error: TS1214

Here, class is a reserved word in TypeScript, and so the code snippet above triggers the TS1214 error.

How to Fix the Error

To resolve this, you can rename the identifier to something that is not a reserved word:

let myClass = "myClass"; // Correct

By changing class to myClass, we avoid the conflict with the reserved word.

Important to Know!

1. Strict Mode: TypeScript files are treated as being in 'strict mode'. This means certain rules apply, helping to catch errors early.
2. Reserved Words: These are keywords that have a special meaning in TypeScript and thus cannot be used as identifiers.

Common Causes of TS1214

Code Example: Incorrect Function Definition

function return() {
    return 42; // Error: TS1214
}

In this case, return is also a reserved word. Renaming the function resolves the error:

function getValue() {
    return 42; // Correct
}

Important to Know!

• Modules and Strict Mode: With modules, TypeScript enforces strict rules that help in maintaining code quality, but they also mean that you need to be careful with how you name your variables and functions.

FAQ Section

Q: What should I do if I still encounter TS1214 after fixing identifiers?

A: Review your code for other potential reserved words, including context such as parameters and variable names.

Q: How can I know if a word is reserved in TypeScript?

A: Consult the official TypeScript documentation which lists all reserved words.

Q: Does TS1214 apply to all JavaScript reserved words?

A: Yes, TypeScript includes JavaScript reserved words and adds some of its own.

Conclusion

Understanding and handling TS1214: Identifier expected. '{0}' is a reserved word in strict mode. Modules are automatically in strict mode. is crucial for any TypeScript developer. By recognizing reserved words and ensuring your identifiers are valid, you can write cleaner, more efficient code. Always remember to double-check your variable names against the list of reserved keywords. For further insights and to keep learning about TypeScript, don’t hesitate to join us!