TS1117: An object literal cannot have multiple properties with the same name

TypeScript is a powerful programming language that builds on JavaScript by adding static types. This means that you can define the type of a variable, function, or object explicitly, which helps catch errors at compile time rather than at runtime. With TypeScript, developers can create more robust and maintainable code by utilizing features like interfaces (which define the structure of an object), enums (which provide a way to define a set of named constants), and various types (like string, number, and custom types).

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In this article, we will discuss a specific TypeScript error: TS1117: An object literal cannot have multiple properties with the same name. Understanding this error can greatly improve your coding practices and help you write cleaner code.

Understanding TS1117: An object literal cannot have multiple properties with the same name

In TypeScript, an object literal is a way to define an object with specific properties. Each property in an object should have a unique name. If you attempt to assign multiple properties with the same name in an object literal, TypeScript will throw an error—specifically, the TS1117 error.

Example that causes the error

Consider the following code snippet:

const person = {
  name: "Alice",
  age: 30,
  name: "Bob" // This will cause TS1117
};

In the example above, we attempted to define an object called person with two properties named name. However, this is not allowed in TypeScript, as it leads to ambiguity about which name property should be used. When you try to compile this code, you will encounter the TS1117 error.

How to fix the error

To resolve the TS1117: An object literal cannot have multiple properties with the same name, you should ensure that each property in your object has a unique name. Here’s a corrected version of the above example:

const person = {
  name: "Alice",
  age: 30,
  nickname: "Bob" // Changed the property name to 'nickname'
};

Now, the object person has a unique set of properties, and the error will no longer occur.

Important to know!

1. Property names in objects must be unique: Always check that you’re not duplicating property names in your object literals to avoid the TS1117 error.
2. Using type definitions can help: By defining types or interfaces for your objects, you can catch these errors during development because TypeScript will enforce the structure you’ve defined.

Important concepts related to the error

• Types: These represent the kind of data that a variable can hold. In TypeScript, you can define basic types (like string, number) or create custom types, which help in structuring data.

• Interfaces: An interface in TypeScript is a way to define the shape of an object by specifying its properties and their types. Here’s an example:
  

  interface Person {
    name: string;
    age: number;
  }

  const person: Person = {
    name: "Alice",
    age: 30
  };

• Enums: Enums allow you to define a collection of related constants as names. This is particularly useful for defining sets of options:

  enum Color {
    Red,
    Green,
    Blue
  }

  const myColor: Color = Color.Red; // Using the enum

Important to know!

1. Type definitions promote code clarity: By using interfaces and enums, you can create clearer and more maintainable code.
2. Leverage the IDE tooling: Most modern IDEs provide features like autocompletion and error highlighting, which can help you catch repetitive property names before compilation.

Conclusion

The TS1117: An object literal cannot have multiple properties with the same name error serves as a reminder to maintain clarity and precision in your code. Always ensure property names in your object literals are unique to avoid confusion. Utilizing TypeScript’s features like types, interfaces, and enums can enhance your coding experience by providing better organization and error-checking.

If you have any questions or would like to learn more about TypeScript, feel free to leave a comment below! Also, consider following my blog for more tips and resources on TypeScript and coding in general.