Functional approach of removing items in a list based on nested property values

I am trying move more towards functional programming in my javascript applications. I currently use the library ramda as a base lib for this.

My desire:

  • Using assertion library outside of testing for list manipulations
  • PureScript does not compose `trace` and `show`
  • If functions in JS are first-class, what allows them to be called before they are defined?
  • Rethinkdb convert an array of objects to a single object
  • Are Church encoded sum types a proper alternative in an untyped language?
  • Get first element of a collection that matches iterator function
    1. Create a function removeUserFromList(username, list) which returns the items in the list that does not match the username.
    2. Make the implementation as short as possible, relying on existing functions in the Ramda library as much as possible.


    A list containing nested user objects:

        providers: {
            github: {
                login: "username1"
        providers: {
            github: {
                login: "username2"

    Acheived so far:

    var list = [{providers: {github: {login: "username1"}}},
                {providers: {github: {login: "username2"}}}];
    var getLoginName = R.useWith(R.path('providers.github.login'));
    var isLoginNameEq = R.useWith(R.eq, getLoginName);
    isLoginNameEq(list[0], "username1") // => true
    //From this point on I am totally clueless, 
    //but I believe I should combine these functions 
    //with R.reject in some way.

    Plunkr demo:


    Is there any better suited function to achieve something similar to R.eq but on nested objects (perhaps R.pathEq)?

  • Functional javascript?
  • Typescript - Higher order function types
  • Javascript functional lazy evaluation example explanation required
  • Async Map with Highland.js
  • What is the in-place alternative to Array.prototype.filter()
  • Function Inside a JavaScript Function Without Declaring it Everytime Anew
  • 3 Solutions collect form web for “Functional approach of removing items in a list based on nested property values”

    I just got a pull request for R.pathEq merged. It won’t be usable until the next release of ramda.js (current version is 0.6.0) but meanwhile you can recreate it like this:

    var pathEq = R.curry(function(path, val, obj) {
        return R.eq(val, R.path(path, obj));

    And then use it like so:

     var rejectThis = 'userName1';
     var myFilter = R.useWith(R.reject, pathEq('providers.github.login'):
     var filteredList = myFilter(rejectThis, users);

    if you don’t need to create the function point-free, you can simply:

    var removeUserFromList= function(name, list) {
        return R.reject(pathEq('providers.github.login', name), list);
    console.log(removeUserFromList('username1', users));

    using @Ludwig Magnussen’s pathEq function.

    Extending the solution from @LudwigMagnusson, a bit, you could do this:

    // terrible name, but I'm never good at that.
    var rejectPathVal = R.curry(function(path, val, list) {
        return R.reject(R.pathEq(path, val), list);
    var filteredList = rejectPathVal('providers.github.login', 'userName1', list);

    And of course you could then use it like:

    var myFilter = rejectPathVal('providers.github.login', 'userName1');
    // ...
    var filteredList = myFilter(list);

    or in any way you choose, given that it’s fully curried. Although as Ludwig pointed out, pathEq is not in the released version of Ramda, you can get it by downloading the HEAD version from Github, or you could use the version Ludwig supplied above.

    But I want to question your requirements a bit. I applaud your attempt to move to a more functional style. I’m one of the authors of Ramda, and think it’s a great choice for a library, but this seems to be unnecessary:

    Make the implementation as short as possible, relying on existing functions in the Ramda
    library as much as possible.

    I would suggest that goals of readability should always trump goals of terseness. Granted, elegance and readability are often tied together with brevity, but “as short as possible” should never be a driving goal.