React double colon meaning JSX usage

react-double-colon-meaning-es6.js

import './login.styl';
import Component from '../components/component.react';
import React from 'react';
import exposeRouter from '../components/exposerouter.react';
import {focusInvalidField} from '../lib/validation';

@exposeRouter
export default class Login extends Component {

  static propTypes = {
    // Something here
  };

  onFormSubmit(e) {
    e.preventDefault();
    const {actions: {auth}, auth: {form}} = this.props;
    // Something here
  }

  redirectAfterLogin() {
    
  }

  render() {
    const {
      actions: {auth: actions},
      auth: {form},
      msg: {auth: {form: msg}}
    } = this.props;

    return (
      <div className="login">
      // This is binding the function onFormSubmit to this fn.bind(this)
        <form onSubmit={::this.onFormSubmit}>
        </form>
      </div>
    );
  }

}

thank you for this