Typed Path

Overview

This small utility helps to extract type information from a TypeScript class, interface or type to use it in your code.

Example:

import {typedPath} from 'typed-path';

type TestType = {
    a: {
        testFunc: () => {result: string};
        b: {
            arrayOfArrays: string[][];
            c: {
                d: number;
            };
        }[];
    };
};

console.log(typedPath<TestType>().a.b[5].c.d.$rawPath);
/*
Outputs
["a", "b", 5, "c", "d"]

*/

Please see other path access methods and how to add custom path access methods below.

The utility might also be used to add type protection to such methods as _.get, _.map, _.set, R.pluck from libraries like lodash, ramda.

It is recommended, though, to use optional chaining instead.

Features

Errors

With typed-path, typescript can check paths and warns you about errors.

Path access methods

Default

.$path

@m-abboud
Also, you can get access to the path string using $path special field.

Like this:

    console.log(tp<TestType>().a.b.c.d.$path); // this will output "a.b.c.d"

.$raw

@dcbrwn
If you need a raw path, which is of type string[] - you can get it using $raw special field.
Deprecated, since it transforms symbols and numbers to strings, which might be not an expected behavior (the method name is "raw"). Please use .$rawPath

    console.log(tp<TestType>().a.b.c.d.$raw); // this will output ["a", "b", "c", "d"]

.$rawPath

If you need a raw path, which is of type (string | number | Symbol)[] - you can get it using $rawPath special field.

    console.log(tp<TestType>().a.b[5].c.d.$rawPath); // this will output ["a", "b", 5, "c", "d"]

The $rawPath is something that you might want to use with the following methods from Ramda, to add type safety on the path:

• R.assocPath,
• R.dissocPath,
• R.hasPath,
• R.path,
• R.pathEq,
• R.pathOr,
• R.paths,
• R.lensPath

Example: https://codesandbox.io/s/typed-path-ramda-assoc-path-x3qby?file=/src/index.ts

Additional handlers

@nick-lvov-dev

You can extend path handlers functionality using additional handlers:

const testAdditionalHandlers = {
    $url: (path: TypedPathKey[]) => path.join('/')
}

console.log(tp<TestType, typeof testAdditionalHandlers>(testAdditionalHandlers).a.b.c.$url); // this will output "a/b/c"

The additional handlers are also chainable:

const testAdditionalHandlers = {
    $abs: (path: TypedPathKey[]) => typedPath<TestType, typeof testAdditionalHandlers>(testAdditionalHandlers, ['', ...path]),
    $url: (path: TypedPathKey[]) => path.join('/'),
    $length: (path: TypedPathKey[]) => path.length
}

console.log(tp<TestType, typeof testAdditionalHandlers>(testAdditionalHandlers).a.b.c.$abs.$url); // this will output "/a/b/c"

Suggestions

Also, typed-path allows typescript to suggest field names for you.

License

Copyright (c) 2021 Oleksandr Beshchuk <[email protected]>
Licensed under the Apache License.