Overriding Typescript Interface Property Type in JS: Tips & Tricks

Introduction

When working with TypeScript interfaces in JavaScript code, you may come across situations where you need to override the type of a specific property. This can be a bit tricky, but with some tips and tricks, you can easily accomplish this task.

Using Type Assertion

One way to override the type of a TypeScript interface property in JavaScript is to use type assertion. This involves using the "as" keyword followed by the desired type.

For example, let's say you have an interface called "Person" with a property called "age" of type "number". If you want to override the type of "age" to be a string in your JavaScript code, you can do the following:

const person = {
  age: "30" // override type to string
} as Person;

In this example, we're using type assertion to override the type of "age" to be a string instead of a number.

Using Partial Interface

Another way to override the type of a TypeScript interface property in JavaScript is to use a partial interface. This involves creating a new interface that extends the original interface but with the specific property's type overridden.

For example, let's say you have the same "Person" interface with an "age" property of type "number". If you want to override the type of "age" to be a string in your JavaScript code using a partial interface, you can do the following:

interface PartialPerson {
  age: string; // override type to string
}

const person: PartialPerson = {
  age: "30"
};

In this example, we're creating a new interface called "PartialPerson" that extends the "Person" interface but with the "age" property's type overridden to be a string. Then, we're using this new interface to create the "person" object with the overridden type.

Conclusion

Overriding the type of a TypeScript interface property in JavaScript may seem daunting at first, but with these tips and tricks, you can easily accomplish this task. Whether you choose to use type assertion or a partial interface, make sure to test your code thoroughly to ensure it works as expected.