README

es6bindall

Simple function to bind multiple methods to an ES6 class's 'this' object. Intended as an equivalent to Backbone/Underscore's _.bindAll() method.

I created this plug-in to get around a problem where an ES6 class method's context is not autobound to the class's object. This is a particular point of pain for ReactJS when using this syntax. (ReactJS's previous .createClass() syntax did autobind a component's methods to the component's own context.)

Problem Code

In the code below, the close() and open() methods, which both call this.setState() will fail. This is because those method's this object is not autobound to the component's context, so this.setState() simply doesn't exist.

class ExampleModal extends React.Component {
  constructor(props) {
    super(props);
  }
  close() {
    this.setState({ showModal: false });
  }

  open(){
    this.setState({ showModal: true });
  }

Workaround 1 - Bind method at call time

One workaround that I've seen suggests that you should bind the method when you're calling it, as shown below:

// Example take from http://egorsmirnov.me/2015/08/16/react-and-es6-part3.html
export default class CartItem extends React.Component {
    render() {
        <button onClick={this.increaseQty.bind(this)} className="button success">+</button>
    }
}

This certainly gives you the most flexibility, since you can call the method as either bound or unbound should you wish. Still, it's a massive pain in the rear to remember to do this every time you call your method.

Workaround 2 - Bind all methods manually in constructor

The code below will work correctly because each method's this is manually bound to the component's context by a separate .bind() call in the component's constructor.

class ExampleModal extends React.Component {
  constructor(props) {
    super(props);
    this.close = this.close.bind(this);
    this.open = this.open.bind(this);
  }
  close() {
    this.setState({ showModal: false });
  }

  open(){
    this.setState({ showModal: true });
  }

While an improvement over Workaround 1, that's still a lot of code to add to your constructor just to bind your methods. And so...

Workaround 3 - Bind all methods manually in constructor with es6bindAll

...and so, I borrowed an idea from Backbone, which has a _.bindAll() function (actually part of Underscore). You can generally call this in your Backbone class constructors in order to bind the methods to the class object. Following that idea, I've created es6BindAll as a simple function that binds a supplied list of method names to a supplied context (this). It takes two arguments:

The context (i.e an object) to which the methods are to be bound.
An array of method names. Those methods must exist in the current component/class, i.e. they can't be external functions.

Example use:

import es6BindAll from "es6bindall";

class ExampleModal extends React.Component {
  constructor(props) {
    super(props);
    es6BindAll(this, ["open", "close"]);
  }
  close() {
    this.setState({ showModal: false });
  }

  open(){
    this.setState({ showModal: true });
  }

Browser/Environment Support

Internet Explorer 9 and upwards, plus all good browsers (i.e. any browser not called Internet Explorer).

Development Instructions

There's not much source code to change, but if you must!

First run npm install to update the dev dependencies, basically the Babel command line tool and its dependences.

The source code is in the src/es6bindall.js file, and is in an es6(ish) kind of format. Run npm run build to have Babel transpile the code to es5 format to the project's main file, i.e. index.js in the root.

Alternatively, you can run npm run start to have Babel watch the src/es6bindall.js file for changes. Babel will then update index.js automatically, whenever you save a change to src/es6bindall.js.

Tests

Tests are built with mocha + chai. Run with npm run test.

Tests check that a test method remains bound to its parent object after its been bound using es6BindAll (i.e. .bind() under the covers), even if the context is being overridden by a .call(). (.bind trumps .call() it seems.)

Update History

Version 0.0.9: 26 Oct 2016 Fixed regression bug with Array handling. Returned to previous array handling code.

Version 0.0.8: 4 Oct 2016

Changed test suite from Mocha/Chai to Tape
Added test for method name supplied as a string

Version 0.0.7: 8 Sept 2016

Added error check for non-existent methods
You can supply a single string method as well as an array

Version 0.0.6: 6 August 2016.

Fixed issue where the function no longer being exported correctly in NodeJS (and possibly elsewhere). This was caused by Babel 6 no longer exporting a default module-exports. Fixed this by adding the babel plugin add-module-exports to the build process. See there for more details of the issue.

Usage no npm install needed!