What does the at symbol (@) do in ES6 javascript? (ECMAScript 2015)

Question

I'm looking at some ES6 code and I don't understand what the @ symbol does when it is placed in front of a variable. The closest thing I could find has something to do with private fields?

Code I was looking at from the redux library:

import React, { Component } from 'react';
import { bindActionCreators } from 'redux';
import { connect } from 'redux/react';
import Counter from '../components/Counter';
import * as CounterActions from '../actions/CounterActions';

@connect(state => ({
  counter: state.counter
}))
export default class CounterApp extends Component {
  render() {
    const { counter, dispatch } = this.props;
    return (
      <Counter counter={counter}
               {...bindActionCreators(CounterActions, dispatch)} />
    );
  }
}

Here is a blog post I found on the topic: https://github.com/zenparsing/es-private-fields

In this blog post all the examples are in the context of a class - what does it mean when the symbol is used within a module?

Answer 1

It's a decorator. It's a proposal to be added to ECMAScript. There are multiple ES6 and ES5 equivalent examples on: javascript-decorators.

Decorators dynamically alter the functionality of a function, method, or class without having to directly use subclasses or change the source code of the function being decorated.

They are commonly used to control access, registration, annotation.