A map is simply a collection of keys with values. What you have is a map with the key categories, and the value {1: ‘a’, 2: ‘b’}. The value does not automatically become an Immutable map just because you place it inside another map. Now, the getIn() function will only “see” other Immutable.js maps. What … Read more
You should use withMutations when you want to group several changes on an object. Because each change creates a clone, several changes in a row cause several clones. Use withMutations to apply several changes then clone once at the end. A clone at every step means that you are reading the entire list for each … Read more
I’m the author of Immutable.js (and a fan of Lazy.js). Does Lazy.js and Immutable.js’s Seq use short-cut fusion? No, not exactly. But they do remove intermediate representation of operation results. Short-cut fusion is a code compilation/transpilation technique. Your example is a good one: var a = [1,2,3,4,5].map(square).map(increment); Transpiled: var a = [1,2,3,4,5].map(compose(square, increment)); Lazy.js and … Read more
You reducer doesn’t have a default action in switch statement. Which is why even though you mentioned the initial state in reducer params, undefined is returned as store initial state import React from ‘react’; import {Map,fromJS} from ‘immutable’; const reducer = (state = Map() ,action) => { switch(action.type){ case ‘SET_STATE’: return state.merge(action.state); default: return state; … Read more
The short answer is that the representation of data structures used by Immutable.js requires a lot of additional overhead to iterate through the elements of a List, compared to a native JS array. Benchmarking Immutable.List.find and Array.find Your benchmark is good, but we can simplify matters a bit by getting rid of the nested map; … Read more
You are correct about merge. Merge will update the index with the current value of the merging list. So in your case you had [0] = 1 and merged it with [0] = 2 [1] = 3 which ended up overwriting [0]=1 with [0]=2, and then set [1]=3 resulting in your observed [2,3] array after … Read more
First, idiomatic Redux encourages you to “normalize” your state and flatten it as much as possible. Use objects keyed by item IDs to allow direct lookups of items, use arrays of IDs to denote ordering, and anywhere that one item needs to refer to another, it only stores the ID of the other item instead … Read more
I don’t think you understood what immutablejs offers. It’s not a library which just turns your objects immutable, it’s a library around working with immutable values. Without simply repeating their docs and mission statement, I’ll state two things it provides: Types. They implemented (immutable) infinite ranges, stacks, ordered sets, lists, … All of their types … Read more
It is possible to use PropTypes.oneOf([null]).isRequired. It should allow null, and nothing else. You can combine that with any other type: PropTypes.oneOfType([ PropTypes.string.isRequired, PropTypes.oneOf([null]).isRequired, ]).isRequired Edit: I just had this prop type fail for me when given a null prop using prop-types 15.7.2, so I’m not sure this works anymore (if it ever did?). I … Read more
TL;DR; No, but using Records you can get Flow to typecheck the shape but not the types. Longform The correct answer would be: no, since maps don’t have shapes (at least in Flow and Immutable). But Immutable does have a type for “Maps” with shapes. That would be Records. But for reasons described below (since … Read more