No index signature with a parameter of type 'string' was found on type '

This error occurs when you attempt to access a property on an object using a string variable as the key, but the object type does not have an index signature that allows for this type of access.

In TypeScript, an index signature allows for dynamic access to an object's properties using a string or numeric key. For example, the following interface defines an index signature for a type that has string keys and any value:

interface MyObject {
  [key: string]: any;
}

If you try to access a property on an object that does not have an index signature, TypeScript will throw the "No index signature with a parameter of type 'string' was found on type" error.

To fix this error, you can add an index signature to the object type, or explicitly define the property key as a string literal. For example:

interface MyObject {
  [key: string]: any;
  foo: string;
}

const myObj: MyObject = { foo: 'bar' };

// This works:
const prop1 = myObj.foo;

// This throws an error:
const key = 'foo';
const prop2 = myObj[key]; // No index signature with a parameter of type 'string' was found on type 'MyObject'

To fix the error in the above example, you can either add an index signature to `MyObject`, or explicitly define the property key as a string literal:

interface MyObject {
  [key: string]: any;
  foo: string;
}

const myObj: MyObject = { foo: 'bar' };

// This works:
const prop1 = myObj.foo;

// This works too:
const key = 'foo';
const prop2 = myObj[key as keyof MyObject];