How to use arrow functions (public class fields) as class methods?

Question

I'm new to using ES6 classes with React, previously I've been binding my methods to the current object (show in first example), but does ES6 allow me to permanently bind a class function to a class instance with arrows? (Useful when passing as a callback function.) I get errors when I try to use them as you can with CoffeeScript:

class SomeClass extends React.Component {

  // Instead of this
  constructor(){
    this.handleInputChange = this.handleInputChange.bind(this)
  }

  // Can I somehow do this? Am i just getting the syntax wrong?
  handleInputChange (val) => {
    console.log('selectionMade: ', val);
  }

So that if I were to pass SomeClass.handleInputChange to, for instance setTimeout, it would be scoped to the class instance, and not the window object.

Answer 1

Your syntax is slightly off, just missing an equals sign after the property name.

class SomeClass extends React.Component {
  handleInputChange = (val) => {
    console.log('selectionMade: ', val);
  }
}

This is an experimental feature. You will need to enable experimental features in Babel to get this to compile. Here is a demo with experimental enabled.

To use experimental features in babel you can install the relevant plugin from here. For this specific feature, you need the transform-class-properties plugin:

{
  "plugins": [
    "transform-class-properties"
  ]
}

You can read more about the proposal for Class Fields and Static Properties here

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