TypeScript TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'

Question

Im getting this compilation error in my Angular 2 app:

TS7015: Element implicitly has an \'any\' type because index expression is not of type \'number\'.
         


        

Answer 1

I was actually working with React and I got this error when I assigned an object's property through a custom key (i.e. myObj[myKey] = ). To resolve it, I simply used as keyof:

interface IMyObj { title: string; content: string; }
const myObj: IMyObj = { title: 'Hi', content: 'Hope all is well' };
const myKey: string = 'content';

myObj[myKey as keyof IMyObj] = 'All is great now!';

This explicitly tells Typescript that your custom string (myKey) belongs to the group of properties from an interface/type you used for declaring your object (myObj).

P.S.: another way to get the property's value is shown on a closed Typescript's issue on Github through extends:

interface IMyObj {
  title: string;
  content: string;
}

const myObj: IMyObj = { title: 'Hi', content: 'Hope all is well' };
const myKey: string = 'content';

const getKeyValue = (obj: T) => (key: U) =>
  obj[key];
console.log(getKeyValue(myObj)(myKey));