What is the return type of lodash's get in TypeScript?

In TypeScript, the return type of Lodash's _.get function is dynamically determined based on the type of the object being accessed and the specified path. It's a bit more complex than a simple type due to its flexibility in handling nested properties and default values.

Here's a breakdown of how it works:

1. Generic Type Inference:

Lodash's get function utilizes TypeScript's powerful generic type inference to determine the return type. If a specific type can be inferred from the object and path, it will use that.

2. Default Value Influence:

The default value, if provided, plays a critical role. If no default value is given and the path doesn't exist within the object, undefined is returned and the type reflects this. When a default value is provided the return type is then the type of the default value or potentially undefined if the path can still resolve to an undefined.

3. Potential for undefined:

Regardless of other types, the return type will always include undefined because _.get can return undefined if the specified path does not exist in the object or if any step along the path fails.

4. Example with Explicit Types:

Let's examine different use cases:

// Example object
interface User {
  profile?: {
   name?: string;
   age?: number;
  };
}

const user: User = {
  profile: { name: "John", age: 30 },
};

import { get } from 'lodash';

// Inferring type string | undefined (profile.name exists)
const userName = get(user, 'profile.name');
// Inferring type number | undefined (profile.age exists)
const userAge = get(user, 'profile.age');

// Inferring type undefined because path does not exist const userCity = get(user, 'profile.city');

// Using default Value. Type will be string
const userCityDefault = get(user, 'profile.city','Unknown City');

// Example when path is incorrect, type is undefined
const userPhone = get(user, 'profile.phones.mobile');


5. Best Practices:

To make your code more type-safe, particularly with complex object structures, you may want to strongly type or use explicit types in your TypeScript code and use more specific checks before utilizing the return value of _.get.

In summary, Lodash's _.get function in TypeScript returns a union type that includes the inferred type of the value at the specified path and undefined, or if a default value is provided it will be the type of default value and undefined

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