How bind works

bind.js

// This code doesn't make any sense.
// Just for pedagogical purposes.
class HelloComponent {
  constructor(id) {
    this.button = document.getElementById(id);
    this.bindLog = this.log.bind(this);
    
    // Use the bind version of log. It ties log to the object we are creating.
    document.addEventListener('click', this.bindLog);
    
    // Log function gets automatically bound to the DOM node that's being clicked
    // There is no setState method at that HTMLElement so an error is thrown.
    document.addEventListener('click', this.log); 
  }
  setState(newState) {
    console.log(this);
  }
  log() {
    console.log('clicked');
    this.setState({newState: 1});
  }
}