Typescript is giving error when getting object using a variable/constant

I have an object like this:

const obj = {
user_name: 'user2',
user_desc: 'desc 2'
}

Now I’m calling an onclick function that specifies which parameter to get from the object

function myFunction (key_name : string) {
// as my constant is of type object, I can get data from keys as
console.log(obj[key_name])
}

My function is running fine but typescript is giving me an error

Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type ‘{}’

How do I go about getting rid of this error?
Thanks

>Solution :

You can create an interface to describe data shapes

interface Obj {
  user_name: string;
  user_desc: string;
}

const obj: Obj = {
  user_name: 'user2',
  user_desc: 'desc 2',
};

function myFunction(key_name: keyof Obj) {
  console.log(obj[key_name]);
}

myFunction('user_name');