Ecosyste.ms: Awesome
An open API service indexing awesome lists of open source software.
https://github.com/alpacatravel/object-assign-reducer
A utility to perform object.assign with a series of rules that can offer state transitions
https://github.com/alpacatravel/object-assign-reducer
Last synced: about 1 month ago
JSON representation
A utility to perform object.assign with a series of rules that can offer state transitions
- Host: GitHub
- URL: https://github.com/alpacatravel/object-assign-reducer
- Owner: AlpacaTravel
- License: mit
- Created: 2020-06-12T03:08:16.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2023-01-06T08:40:45.000Z (almost 2 years ago)
- Last Synced: 2023-02-28T21:56:46.336Z (almost 2 years ago)
- Language: JavaScript
- Homepage:
- Size: 763 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Object Assign Reducer
[](https://travis-ci.org/AlpacaTravel/object-assign-reducer)[](https://coveralls.io/github/AlpacaTravel/object-assign-reducer?branch=master)
A "hideous" utility to reduce an object assignment of properties into a new state.
This exists for a use case where you wish to apply an object property and automatically remove or update other properties based on a set of rules. In this case, we need to be able to target a number of conditions, such as describing edge-cases and compatible states to apply a criteria based on the resulting object.
A couple of special things:
- If the supplied rule matches, but then does not transition the object away from a match, it will throw an error
- Rules are applied continually until there is no further state transitions
```javascript
const { assign } = require("@alpaca-travel/object-assign-reducer");
// State before
const state = {
category: "eat",
subCategory: "restaurant",
tags: ["tag1"],
};
// Changing state
const changeState = { category: "stay" };
// We want to eliminate the subcategory on change
// Traditional assign has not subtle rules
// Object.assign({}, state, apply);
// { category: stay, subCategory: restaurant }
// Describing rules as collections of match/perform
const rules = [
{
// Setup a matching rules to take the before value, and the after value
// Return true when we want to match against this rule
match: (before, after) =>
// Category does has changed
before.category !== after.category &&
// Has a subcategory
before.subCategory &&
after.subCategory,
// Perform a modification to the object
perform: (obj) => {
// Poor mans clone
const val = JSON.parse(JSON.stringify(obj));
delete val.subCategory;
return val;
},
},
// ... More rules added here
];
const value = assign({ rules })(state, changeState);
// { category: 'stay' }
```
## Fexp-js Lang Feature
This is as a language enhancement for fexp-js scripting.
[](https://codesandbox.io/s/silent-sun-yugzk?fontsize=14&hidenavigation=1&theme=dark)
```javascript
const { parse, langs } = require("@alpaca-travel/fexp-js");
const stdLang = require("@alpaca-travel/fexp-js-lang");
const {
lang: newLangFeatures,
} = require("@alpaca-travel/object-assign-reducer");
// Define this in YAML/JSON, and can be external to your application code
const expr = [
"reducer-assign",
// Matcher function
[
"fn",
[
// All conditions are true in order to perform this action
"all",
// Categories don't match
// fn-arg 0 = before
// fn-arg 1 = after
[
"!=",
["get", "category", ["fn-arg", 0]],
["get", "category", ["fn-arg", 1]],
],
// They have sub-categories
["exists", ["get", "subCategory", ["fn-arg", 0]]],
["exists", ["get", "subCategory", ["fn-arg", 1]]],
],
],
// Action to remove the sub category
["fn", ["remove", "subCategory"]],
// ... more can go here
// The context of the second argument
["fn-arg", 1],
];
// Fn now contains all the rules
const fn = parse(expr, langs(stdLang, newLangFeatures));
// State before
const state = {
category: "eat",
subCategory: "restaurant",
tags: ["tag1"],
};
// Changing state
const changeState = { category: "stay" };
const result = fn(state, changeState);
// { category: 'eat', tags: ['tag1'] }
```