Typescript is giving error. Element implicitly has an 'any' type because expression of type 'string' can't be used to index type

Question

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

Does this answer your question? Element implicitly has an 'any' type because expression of type 'string' can't be used to index — Vikram Deshmukh
– Vikram Deshmukh, Commented May 9, 2023 at 20:35

Sanka Sanjeeva · Accepted Answer · 2022-09-22 09:59:35Z

2

You can create an interface to describe your data shape

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');

edited Sep 22, 2022 at 9:59

answered Sep 22, 2022 at 9:46

Sanka Sanjeeva

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Comments

nightElf · Accepted Answer · 2022-09-22 09:43:35Z

2

Because of the obj that you have created, the keys are inferred by typescript.

There are two ways of solving this:

Give type to the obj

const obj: Record<string, string> = {
 user_name: 'user2',
 user_desc: 'desc 2'
}

---- OR -----

Give type to your function param

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

answered Sep 22, 2022 at 9:43

nightElf

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