How to check if an object implements an interface at runtime with TypeScript?

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Sometimes, we want to check if an object implements an interface at runtime with TypeScript.

In this article, we’ll look at how to check if an object implements an interface at runtime with TypeScript.

To check if an object implements an interface at runtime with TypeScript, we can create our own function.

For instance, we write

interface Test {
  prop: number;
}

function isTest(arg: any): arg is Test {
  return typeof arg?.prop === "number";
}

to define the isTest function that returns the arg is Test type.

This lets the TypeScript compiler know that it’s a type guard function.

Then we check if arg.prop is a number with typeof in it and return the result.

To check if an object implements an interface at runtime with TypeScript, we can create our own function.

By John Au-Yeung