ramda.js

I used to write something like _.map(items, (item, index) => {}); with lodash. Usually I don't need index but sometimes it's useful. I'm migrating to Ramda now: R.map((item, index) => {}, items); index is undefined . Sure, I can create variable index in upper scope and increment it every time in map body but it's kinda wrong from FP point of view that Ramda stands for. So is there's any build in way of getting iteration index? Check out addIndex : Creates a new list iteration function from an existing one by adding two new parameters to its callback function: the current index, and the entire

Using Ramda.js (and lenses), I want to modify the JavaScript object below to change "NAME:VERSION1" to "NAME:VERSION2" for the object that has ID= "/1/B/i". I want to use a lens because I want to just change one deeply nested value, but otherwise retain the entire structure unchanged. I don't want to use lensIndex because I never know what order the arrays will be in, so instead, I want to "find" the object in an array by looking for its "id" fields. Can I do this with lenses, or should I do it a different way? { "id": "/1", "groups": [ { "id": "/1/A", "apps": [ { "id": "/1/A/i", "more nested

I want to take an array [1, 2, 3] and return [1, 2, 3, 1] . I'm using Ramda, and I can get the desired result like this: const fn = arr => R.append(R.prop(0, arr), arr); But I'd like to do it point-free. Here's the closest I've gotten: const fn = R.compose(R.append, R.prop(0)); fn(arr)(arr) But that looks silly. What am I missing? Thanks! converge can be very helpful for things like this. const rotate = R.converge(R.append, [R.head, R.identity]) rotate([1, 2, 3]); //=> [1, 2, 3, 1] The S combinator is useful here: S.S(S.C(R.append), R.head, [1, 2, 3]); // => [1, 2, 3, 1] 来源： https:/

In case it matters this is about functional programming in JavaScript and in my examples I’ll be using Ramda. While everybody at work has fully embraced functional programming, there’s also a lot of discussions around how to do it “right”. These two functions will do exactly the same thing: take a list and return a new list in which all strings have been trimmed. // data-centric style const trimList = list => R.map(R.trim, list); // point-free style const trimList = R.map(R.trim); So far so good. However with a more complex example, the difference between the two styles is striking: take a

I have 2 arrays a = [2,3,1,4] b = [{id: 1}, {id: 2}, {id: 3}, {id: 4}] How do I get b sorted based on a ? My desired output would be c = [{id: 2}, {id: 3}, {id: 1}, {id: 4}] I would prefer to use Ramda or regular JS. Ramda really shines for these types of problems. Where the size of the data is small, we can use a simple reduce function, and indexOf helper. // match id of object to required index and insert var sortInsert = function (acc, cur) { var toIdx = R.indexOf(cur.id, a); acc[toIdx] = cur; return acc; }; // point-free sort function created var sort = R.reduce(sortInsert, []); // execute

I have a situation where I need to do this: const f = (obj) => assoc('list', createList(obj), obj) Due to the fact that I need the argument for the second and the third parameter, prohibits me from doing something like: const f = assoc('list', somehowGetObj()) I also tried this, but that didn't work: const f = assoc('list', createList(__)) const f = converge(assoc, [createList, identity]) Is there a proper way to do this by currying? Another option is chain(createList, assoc('list')) which you can see in action on the Ramda REPL . Update For further explanation of how this works, I'll use the