Interface for associative object array in TypeScript

Question

I have an object like so:

var obj = {
    key1: "apple",
    key2: true,
    key3: 123,
    .
    .
    .
    key{n}: ...
}

So obj can contain any number of named keys, but the values must all be either string, bool, or number.

How do I declare the type of obj as an interface in TypeScript? Can I declare an associative array (or variadic tuple) of a union type or something similar?

Answer 1

Yes, you can use an index signature:

interface MyType {
    [key: string]: string | boolean | number;
}

var obj: MyType = {
    key1: "apple",
    key2: true,
    key3: 123
};