Armentage Armentage - 3 months ago 6
TypeScript Question

Enforcing the type of the indexed members of a Typescript object?

I would like to store a mapping of string -> string in a Typescript object, and enforce that all of the keys map to strings. For example:

var stuff = {};
stuff["a"] = "foo"; // okay
stuff["b"] = "bar"; // okay
stuff["c"] = false; // ERROR! bool != string


Is there a way for me to enforce that the values must be strings (or whatever type..)?

Answer
var stuff: { [s: string]: string; } = {};
stuff['a'] = ''; // ok
stuff['a'] = 4;  // error

// ... or, if you're using this a lot and don't want to type so much ...
interface StringMap { [s: string]: string; }
var stuff2: StringMap = { };
// same as above