Type X cannot be used to index type error on type for object property 2 levels deep

If you are working with TypeScript and encounter the error “Type X cannot be used to index type error on type for object property 2 levels deep,” you are not alone. This error typically occurs when you try to access a property of an object that is nested two levels deep using a type that is not compatible with the index signature of the object. In this blog post, we will explore two possible solutions to resolve this error.

Solution 1: Using type assertions

One way to resolve the “Type X cannot be used to index type error” is by using type assertions. Type assertions allow you to override the type system and tell TypeScript that you know the type of a value better than it does.

Here’s an example:


interface MyObject {
  prop1: {
    prop2: {
      prop3: string;
    };
  };
}

const obj: MyObject = {
  prop1: {
    prop2: {
      prop3: "Hello, TypeScript!";
    },
  },
};

const value = obj.prop1.prop2["prop3" as keyof typeof obj.prop1.prop2];
console.log(value); // Output: Hello, TypeScript!

In the above example, we use a type assertion ("prop3" as keyof typeof obj.prop1.prop2) to tell TypeScript that we want to access the property prop3 of the object obj.prop1.prop2 using the string literal type "prop3". This helps TypeScript understand that we are accessing a valid property and resolves the error.

Solution 2: Using optional chaining

Another solution to the “Type X cannot be used to index type error” is by using optional chaining. Optional chaining allows you to safely access nested properties without the need for type assertions.

Here’s an example:


interface MyObject {
  prop1?: {
    prop2?: {
      prop3?: string;
    };
  };
}

const obj: MyObject = {
  prop1: {
    prop2: {
      prop3: "Hello, TypeScript!";
    },
  },
};

const value = obj.prop1?.prop2?.prop3;
console.log(value); // Output: Hello, TypeScript!

In the above example, we use optional chaining (?.) to access the nested property prop3 of the object obj.prop1.prop2. Optional chaining ensures that if any intermediate property is undefined or null, the expression short-circuits and returns undefined, preventing the error from occurring.

By using either type assertions or optional chaining, you can resolve the “Type X cannot be used to index type error on type for object property 2 levels deep” and access the nested properties of an object without encountering any type errors.

Remember to choose the solution that best fits your use case and coding style. Happy coding with TypeScript!

Type X cannot be used to index type error on type for object property 2 levels deep