Example of using keyof in typescript

keyof.ts

function filter<T, K extends keyof T>(obj : T, keys : [K], value: any) : boolean {
    return keys.some(key => obj[key] === value);
}

let person = {
    name: "bos",
    firstName: "jos"
}

filter(person, ['firstName', "namee"], "jos");
/*
ERROR: Argument of type '["firstName", "namee"]' is not assignable to parameter of type '["firstName" | "name"]'.
*/

Instead of value: any you could also use T[K]:

function filter<T, K extends keyof T>(obj : T, keys : [K], value: T[K]) : boolean {
    return keys.some(key => obj[key] === value);
}

let person = {
    name: "bos",
    firstName: "jos"
}

filter(person, ['firstName', "name"], 1);
/*
ERROR: Argument of type '1' is not assignable to parameter of type 'string'.
*/