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Discussion on: What the beep is 'this' in JavaScript

brityhemming profile image
Brit Hemming Author

Hey Sebastian, Thanks for your comment. Could you give me an example of where implicit binding didn't work for you?

beitist profile image
Sebastian Stüwe

Hi Brit,

sorry for the late response - I couldn't exactly remember where it happened, but now I found the problem:

Assume the following micro-example:

START_NODE = document.getElementById('start');

class Major {
  constructor() {
    this.minor = new Minor();
    this.handler = '';

  initHandler() {
    this.handler = new Handler();

  listenToHandler(parameter) {
    this.minor.someValue = parameter;


class Minor {
  constructor() {
    this.someValue = '';

class Handler {
  constructor() {
    this.button = document.createElement('button');
    this.button.innerText = 'Click!';
    this.button.addEventListener('click', major.listenToHandler.bind(3));

let major = new Major();
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Here's a possible corresponding html-file:

<!DOCTYPE html>
    <script src='bindproblem.js' defer></script>
    <div id='start'></div>
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You'll notice that JS throws a TypeError which must have something to do with the scope, I presume. I've usually found workarounds, but I do not like them. I'd like to really understand the problem.


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brityhemming profile image
Brit Hemming Author

This is likely a scope issue. A couple of things to know about classes:

  • classes are not hoisted - that means if we are putting our information above a class we have referenced it will not work
  • they use strict - it prevents window binding, forces us to write cleaner code with errors if we do not
  • Methods are a special syntax
  • A constructor function is visible

In your case point 1 is the issue - classes are not hoisted. You've created Handler below where you are invoking it.

Here's a codepen where I explain classes a little deeper. Hopefully that's helpful :)