javascript - TypeScript - Element implicitly has an 'any' type because expression of type 'string' can't be used to index type

Question

Let's say I have this:

const color = {
    red: null,
    green: null,
    blue: null
};

const newColor = ['red', 'green', 'blue'].filter(e => color[e]);

The error is in color[e] near the bottom with:

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ red: null; green: null; blue: null; }'. No index signature with a parameter of type 'string' was found on type '{ red: null; green: null; blue: null; }'.

I tried looking everywhere on TypeScript docs, but how the heck am I suppose to interface this so it can accept color[e]?

Answer 1

You can declare colors as any to tell TypeScript to get off your back on this one (aka explicit any):

const color : any = {
    red: null,
    green: null,
    blue: null
};

But if possible, strong typing is preferable:

const color : { [key: string]: any } = {
    red: null,
    green: null,
    blue: null
};

More information on indexing in TypeScript: Index Signatures

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EDIT: In this answer to a similar question, the author suggest using a Map<,> -- if that fits your use-case.