Cortex is a Javascript library for centrally managing data with React.

Key features:

supports deeply nested data
exposes changes for every data node
performs efficient batch updates and rewrapping
has built-in methods for working with arrays and hashes
written in ES6

Demos

file system (arbitrarily deep structure of a single component type)

Quickstart

Initialize a cortex object

var data = {a: 100, b: [1, 2, 3]};

var cortex = new Cortex(data, function(updatedCortex) {
  //trigger your React component to update props
});

Get a nested cortex object

cortex.a

//Also works
cortex['a']

Get a nested cortex element in an array

cortex.b[0]

Get the actual value

cortex.a.getValue()
// ==> 100

Change data

cortex.a.set(200);
cortex.a.getValue();
// ==> 200

Change data from root object

cortex.set({a: 300})
cortex.getValue()
// ==> {a: 300}

Get the changes

cortex.getChanges(); // => [{type: "update", path: ['a'], oldValue: 200, newValue: 300}]

// changes are available at every node at any level. Note the difference in path
cortex.a.getChanges(); // => [{type: "update", path: [], oldValue: 200, newValue: 300}]

// subtree without changes returns empty array
cortex.b.getChanges(); // => []

Alternatively you can also check whether a node changes

cortex.didChange() // => true

cortex.didChange('a') // => true
cortex.didChange('b') // => false

//same as above
cortex.a.didChange()  // => true
cortex.b.didChange()  // => false

** You SHOULD NOT use getChanges and didChange to implement shouldComponentUpdate unless your components ONLY rely on cortex object to rerender. The reason is these changes are computed on cortex update and retained until the next update, so if your non-cortex props or state change then your nextProps, nextState would still contain the cortex changes of the previous cycle. This may incorrectly return true and results in your components updating more frequent than they should be.

Add callbacks

cortex.on("update", myCallback);

Remove callback

cortex.off("update", myCallback);

Remove all callbacks

cortex.off("update");

Overview

In React's world data flows in one direction from the top down. That means if you want to make a change, change it at the source and let it propagate down the chain. But what happens when a child component needs to update the data? React's official guideline is to use callback for communication between parent and child components.

However, this simply isn't sustainable even for trivially nested data. Imagine a Restaurant app in which the Restaurant has many Orders, each has many Items, each of which has many Modifiers. If you want to update a Modifier from 'medium rare' to 'well-done' you'd have to pass the data changes several levels up. This is not only awkward but also creates unnecessary extra code in each component in the chain only for the purpose of passing data upstream.

Cortex's goal is to support arbitrarily deep data structures without requiring you to pass callbacks down the chain. Cortex achieves this by thinly wrapping your data in an object that contains the key for locating each nested piece of data as accessed from the top level. When you change the data, internally Cortex passes the new value along with its location key to update the data at the source.

Basic example

The following example has two components Order and Item components. An Order contains an array of Items, and each Item can increase its own quantity attribute.

var Item = React.createClass({
  increase: function() {
    var quantity = this.props.item.quantity.getValue();
    this.props.item.quantity.set(quantity + 1);
  },
  subTotal: function() {
    return this.props.item.quantity.getValue() * this.props.item.price.getValue();
  },
  render: function() {
    return(
      <div className="item">
        <a href="#" onClick={this.increase}>+</a>
        <span>{this.props.item.quantity.getValue()}</span>
        <span>{this.props.item.name.getValue()}</span>
        <span>${this.subTotal()}</span>
      </div>
    );
  }
});

var Order = React.createClass({
  render: function() {
    var items = this.props.order.map(function(item){
      return <Item item={item} />;
    });
    return(
      <div>{items}</div>
    );
  }
});

var orderData = [
      {name: "Burger", quantity: 2, price: 5.0},
      {name: "Salad", quantity: 1, price: 4.50},
      {name: "Coke", quantity: 3, price: 1.50}
    ];

//Initialize cortex with data and pass in a callback to run when data is updated.
var orderCortex = new Cortex(orderData);

var orderComponent = React.renderComponent(
  <Order order={orderCortex} />, document.getElementById("order")
);

orderCortex.on("update", function(updatedOrder) {
  orderComponent.setProps({order: updatedOrder});
});

First we initialize cortex with:

var orderCortex = new Cortex(orderData);

Then it's passed into the Order component to render the Item components.

We set a callback to run on update event using

orderCortex.on("update", function(updatedOrder) {
  orderComponent.setProps({order: updatedOrder});
});

In Item component, note that we display the quantity value with this.props.item.quantity.getValue(). This is because this.props.item.quantity only gives us the wrapper of the quantity attribute, we need to call getValue() to get the actual value.

In increase method, we use this.props.item.quantity.set(quantity + 1) to add 1 to the current quantity value.

Cortex API

Initialize:

new Cortex(data, function() {
  //trigger your React component to update
});

Instance methods:

Method                    | Description
--------------------------|:-------------------
`getValue()`              | Returns the actual value
`val()`                   | Alias for `getValue`
`set(value)`              | Changes the value and rewrap the subtree.
`remove()`                | Self destruct method: remove self from parent if nested, set value to undefined if root level.
`on("update", callback)` | Add a callback to run on update event (only available on root object)
`off("update", callback)`| Remove a callback. If no callback is specified, all existing callbacks will be removed (only available on root object)
`getChanges()`            | Returns array of changes. Each change include the change type (either 'new', 'update', or 'delete'), the path (array of keys to the changed subtree), oldValue, and newValue
`didChange(key)`          | Returns boolean value whether a change was made. key is an optional argument. When key provided, it checks whether changes occur in the key subtree. When not provided, it checks whether any change was made on the current node.

Cortex wrapper of array data has the following methods:

Method                         | Description
-------------------------------|:----------------------
`count()`                      | Returns length of nested wrappers
`forEach(callback)`            | Iterates over all elements. The callback accepts the following input `(wrapperElement, index, wrapperArray)`
`map(callback)`                | Returns a new array as returned by the callback. Callback accepts same input as forEach callback
`filter(callback, thisArg)`    | Returns a new array of wrappers whose elements satisfy condition return by callback.
`find(callback)`               | Returns the first wrapper element that meets the condition returned by callback. Callback accepts same input as forEach callback.
`findIndex(callback)`          | Returns index of first wrapper element that meets condition returned callback. Callback accepts same input as forEach callback.
`push(value)`                  | Inserts and rewrap the value at the end of the array.
`pop()`                        | Removes the last element in the array
`unshift(value)`               | Inserts and rewrap the value at the front of the array.
`shift()`                      | Removes the first element in the array
`insertAt(index, [value])`     | Inserts a value or an array of values starting at specified index.
`removeAt(index, howMany = 1)` | Removes specified number of elements starting at index location. By default it removes 1 element if number of elements to be removed isn't specified.

Cortex wrapper of hash data has the following methods:

Methods                        | Description
-------------------------------|:------------------------
`keys()`                       | Returns the array of keys
`values()`                     | Returns the array of values
`hasKey(key)`                  | Returns boolean value whether the key exists
`forEach(callback)`            | Iterates over every key and value pair. The callback accepts the following inputs `(key, wrapperElement)`
`destroy(key)`                 | Removes the specified key and value pair
`add(key, value)`              | Adds the specified key and value pair

CDN

cortex.0.6.2.js cortex.0.6.2.min.js

Install via Bower

bower install cortexjs

Reference the js file

<script src="/bower_components/cortexjs/build/cortex.js"></script>

Using cortex with node.js

Install via npm

npm install cortexjs

Use it:

Cortex = require("cortexjs");

wrappedData = new Cortex({mydata: 1});
console.log(wrappedData.mydata.getValue()); //1

wrappedData.mydata.set(100);
console.log(wrappedData.mydata.getValue()); //100

Install via spm

spm install cortexjs

Building Cortex

To build Cortex:

gulp

To run test:

gulp test

To compile jsx files in examples into js files:

gulp react

Design & Optimizations

Besides providing the convenience of allowing you to update data from any level, Cortex also has several optimizations that help boost performance.

1. Deep comparison between old and new values

When you issue a set(newValue) call, no data actually changes at that point. What happens internally is the wrapper being called publishes a notification to the master cortex wrapper passing along a payload consisting of the path for locating the data and the new value (Yes, there is a pub/sub system within Cortex.) The master wrapper then performs a deep comparison between the old and new data to determine whether it should trigger the update action. If no change was made, the process just exits without touching the data nor invoking the callbacks.

Deep comparison may sound costly but in practice when you call set(newValue) the newValue usually isn't deeply nested (if it is and the actual change is many layers deep then you should consider calling set(newValue) on the wrapper at the level that the change actually occurs.) In some situations where you have to pass in arbirarily deeply nested value the comparison work is still worth it because it can potentially save you from unnecessarily rewrapping and triggering React to update.

2. Batch rewrap and invoke callbacks once for multiple updates

When multiple updates occur at the same time, it will result in the same number of data rewrapping and callback invocations, which usually involve triggering React to update that same number of times. While React has good diffing algorithm for efficiently redrawing the DOM it would be even more efficient if React doesn't have to perform DOM comparison mutliple times. Cortex avoids triggering React by running callback only once for updates happening at the same time. This is especially useful when an array is being updated one element at a time or a deeply nested piece of data change at multiple levels.

spmjs / cortex Goto Github PK

cortex's Introduction