TypeScript: Object.keys return string[]

by

Object.keys returns a string[]. This is by design as described in this issue

This is intentional. Types in TS are open ended. So keysof will likely be less than all properties you would get at runtime.

There are several solution, the simplest one is to just use a type assertion:

const v = {
    a: 1,
    b: 2
};

var values = (Object.keys(v) as Array<keyof typeof v>).reduce((accumulator, current) => {
    accumulator.push(v[current]);
    return accumulator;
}, [] as (typeof v[keyof typeof v])[]);

You can also create an alias for keys in Object that will return the type you want:

export const v = {
    a: 1,
    b: 2
};

declare global {
    interface ObjectConstructor {
        typedKeys<T>(obj: T): Array<keyof T>
    }
}
Object.typedKeys = Object.keys as any

var values = Object.typedKeys(v).reduce((accumulator, current) => {
    accumulator.push(v[current]);
    return accumulator;
}, [] as (typeof v[keyof typeof v])[]);

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