Racor

Tool to copy values from given key/path of an object, into another.

This basically....

Is a dead-simple JavaScript hand-changing utility for data, mostly JSON.

• Gets a value from given object, at given path
• Applies a pipe function in between (optionally)
• Sets that value to a different object, at a given path

path uses a syntax very similar to lodash set and get, because originally racor used these both.

It passes data from a given path inside the source object [, applies an optional function to it], and set it to a given path inside the destination object.

I'd like to think about it as hose-fitting, because I developed this with an objective in mind: hydrating my schemas with data, in a stylish declarative way.

A racor or raccord is a pipe fitting utility that comes in several forms to achieve different connections.

Since version 1.1.0 the only dependency is deepmerge and has own custom implementations similar to lodash's set and get

Installation

Now available as npm package, so it's an npm install racor away!

(this is actually my first NPM module to be published)

Or build it from source:

git clone ... && cd ... npm install npm run build

Thanks to Rollup (with Babel, Node Resolver, CommonJS and Uglify plugins), this will generate files

• dist/bundle.min.js for usage in the browser. The bundle includes deepmerge.
• lib/racor.js converted to ES5 to use with require() from Node (and maybe browser too, IDK)

Test

After the usual: git clone ... && cd ...

npm install

The npm test command will run a test suite with many different use cases. Take a look at test/racor.test.js for more information.

Usage

Lets say we have a Form that will be generated using JSONSchema through one of the great tools that are out there for it [0].

My Form is an Image upload. I have to associate an Image with a Post, so I ask my API to get me the posts. The response data will probably look like:

{
    "posts": [
        {
            "id": 1,
            "title": "Some"
        }, {
            "id": 2,
            "title": "Some Two"
        }, {
            "id": 3,
            "title": "Some Tre"
        }
    ]
}

Our Image Form schema has a "post" field to establish a relation. And we want to set the options for the dropdown before the Form is rendered.

So we'd do:

const schemas = { schema: { /* properties, whatever */ } };

fetch('/api/posts').then(res => res.json()).then(data => {

    // also we can get it assigned passing the schemas as "output" argument
    let hydratedSchemas = racor({
        src: 'posts',
        pipe: ps => ps.map(p => p.id),
        dst: 'schema.properties.posts.enum'
    }, data, schemas);

    // this particular example pases a "pluck" fn as pipe.
    // we could use a provided shorthand method:
    let hydratedSchemas = racor.pluck("id", {'posts': 'schema.properties.posts.enum'}, data, schemas);

    // also we can do multiple copyings, passing an array of src's and dst's
    let specs = [{
        src: 'posts',
        pipe: ps => ps.map(p => p.id),
        dst: 'schema.properties.posts.enum'
    }, {
        src: 'posts',
        pipe: ps => ps.map(p => p.name),
        dst: 'schema.properties.posts.enumNames'
    }];

    let hydratedSchemas = racor(specs, data, schemas);
});

Pipes

All these specs could easily be stored as text in a database, so the data mappings doesn't have to be hard-coded.

The pipe function could be stored as text too, because the tool supports bring it to live with the new Function() strategy.

So instead of passing a real function we can supply:

...an Array

pipe: ['ps', 'return ps.map(p => p.id)']

...and Object (with args and body keys):

pipe: { args: 'ps', body: 'return ps.map(p => p.id)' }

...or a String (only the body):

pipe: 'return arguments[0].map(p => p.id)'

This is achieved thanks to the JS functionality where you define a function using the Function constructor:

> const sum = new Function('a, b', 'return a + b');
> sum(10, 4);
14

Notice that this actually uses eval so use it at your own risk

Abbreviated usage:

See test file for more complex and varied usage examples

racor.min({'src.path': 'destination.pat'}, data[, base])
racor.fn(t => t.toUpperCase(), { 'data.some': 'someList', 'data.other':'otherList' }, data[, base])
racor.pluck('id', { 'data.posts': 'postIds' }, data[, base]);

Related

[0] I mean React-JSONSchema-Form, JSONSchema-Form (for Angular) or any other, see:
https://json-schema.org/implementations.html#web-ui-generation