The thing is, if you write your own implementations of lodash functions, you then are responsible for maintaining that code, the tests for it (you forgot to include the tests in your article BTW), and the Typescript Types. And the chief use of lodash is to teach devs the kinds of things you can do if you truly think in a functional manner. So some of the more valuable functions are curry and rearg. And the ability to use the different forms of the iteratee shorthand make it really nice to dynamically access arrays and objects with essentially the same syntax across all the methods in the library.