typesafe-deep-paths

A TypeScript utility package to safely access and modify deeply nested properties within objects using typed string paths. Provides type-safe path autocompletion for known paths while allowing fallback values for paths that may not exist.

Features

• Type-safe path autocompletion: Access nested properties with autocompletion for valid paths.
• Fallback support: Define fallback values for paths that may not exist.
• Flexible access: Handles both known and unknown paths in objects.
• Deeply nested property access: Easily get and set deeply nested properties using string paths.

Installation

npm install typesafe-deep-paths

Usage

getPath

The getPath function allows you to retrieve the value of a deeply nested property in an object based on a string path. If the path doesn't exist, you can provide a fallback value. It also supports retrieving values from arrays, returning multiple values if the path leads to an array of items.

Syntax:

getPath<T, P extends Path<T> | string, F>(obj: T, path: P, defaultValue?: F): P extends Path<T> ? any : F;

• T: The object type from which the property is being accessed.
• P: A string representing the path to the property (type-safe if the path exists in the object).
• F: The fallback value type to return if the path does not exist.

Example:

const data = {
    user: {
        profile: {
            name: 'Alice',
            address: {
                street: 'Main St',
                city: 'Somewhere',
            },
        },
        subProfiles: [
            {
                name: 'John',
                address: {
                    street: 'Elm St',
                    city: 'Somewhere else',
                },
            },
            {
                name: 'Robb',
                address: {
                    street: 'Second St',
                    city: 'Another Place',
                },
            },
        ],
    },
};

// Accessing a known path - returns the correct value
const street = getPath(data, 'user.profile.address.street');  // 'Main St'

// Accessing an unknown path - returns the default value
const zipCode = getPath(data, 'user.profile.address.zipCode', '00000');  // '00000' (default value)

// Using fallback with unknown path
const age = getPath(data, 'user.profile.age', 30);  // 30 (default since 'age' is missing)

// Accessing multiple entries in an array - returns an array of values
const cities = getPath(data, 'user.subProfiles.address.city');  // ['Somewhere else', 'Another Place']

// Accessing a property that exists only once in an array - returns a single value
const postcode = getPath(data, 'user.subProfiles.address.postcode');  // '00000' (or your default value if not present)

setPath

The setPath function allows you to set the value of a deeply nested property in an object based on a string path. If intermediate objects in the path do not exist, they will be created automatically.

Syntax:

setPath<T, P extends Path<T>>(obj: T, path: P, value: any): void;

• T: The object type in which the property is being set.
• P: A string representing the path to the property (type-safe).
• value: The value to set at the specified path.

Example:

const data = {
  user: {
    profile: {
      name: 'Alice',
    },
  },
};

// Setting a nested property
setPath(data, 'user.profile.address.street', 'Elm St');
console.log(data.user.profile.address.street);  // 'Elm St'

// Creating intermediate objects while setting a value
setPath(data, 'user.profile.contact.email', '[email protected]');
console.log(data.user.profile.contact.email);  // '[email protected]'

TypeScript Support

The package uses TypeScript's advanced types to provide autocompletion and type checking for known object paths. When accessing a known path, TypeScript will suggest the valid nested keys and check for correct types. For unknown paths, you can use fallback values to ensure safe access.