Using Jquery $(This) With Es6 Arrow Functions (Lexical This Binding)

jQuery and ES6 arrow functions

The basic functionality is trivial: The Event object the handler receives has a currentTarget property which is the same as this:

$(".all-buttons").click(e => console.log(e.currentTarget.innerHTML));

Note this is not the same as e.target:

• target is the element the event is targeted at, whereas
• currentTarget is the element the event is passing through on en route to that target on which this handler was hooked

So for instance, if you have

<div>
    <span>click me</span>
</div>

...and you have a handler hooked to that div, clicking the span will give you e.target = the span, e.currentTarget = the div.

Regarding "other libraries," library recommendations are off-topic for SO. But I'll note that on modern browsers:

• The NodeList returned by the DOM's own querySelectorAll has forEach, which makes it easy to loop over matches (it's also trivial to polyfill on any vaguely-recent browser)
• DOM elements also now have a closest method which makes event delegation with the DOM much simpler than it used to be (and again, can be polyfilled).

Jquery with arrow function

from https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions

An arrow function expression has a shorter syntax than a function
expression and does not bind its own this, arguments, super, or
new.target. These function expressions are best suited for non-method
functions, and they cannot be used as constructors.

ES6 Arrow functions vs ES5: how to know which function to bind `this` to when using ES5 non-arrow function

Why do you use bind(this) with the callback to setTimeout rather than with the counter function?

Because the counter function (which works like a method of the obj object) already has the proper this because you call it like obj.counter() so it gets this from calling it as obj.counter(). Assuming you call counter as obj.counter(), then if you do console.log(this.id) on the first line of the counter() function, it will properly show the id value.

The callback you pass to setTimeout() however has no natural this value unless you use an arrow function or .bind() on the callback function itself because when setTimeout() calls your callback it does not set a specific this value (it just calls your callback as a normal function), therefore the this value goes to the default. That means this will be undefined if running strict mode or the global object if running in loosey-goosey mode inside of the setTimeout() callback.

See the 6 ways that the value of this is set here when calling a function.

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I should also mention that if you did what you were proposing like this:

var obj = {
  id: 42,
  counter: function counter() {
    setTimeout(function() {
      console.log(this.id);
    }, 1000);
  }.bind(this);
};

Not only would it not help the setTimeout() callback at all, but it would also bind the wrong value of this to the counter() method. You would get whatever this was before the var obj definition (also known as the lexical value of this).

What does this refer to in arrow functions in ES6?

Arrow functions capture the this value of the enclosing context

function Person(){
  this.age = 0;

  setInterval(() => {
    this.age++; // |this| properly refers to the person object
  }, 1000);
}

var p = new Person();

So, to directly answer your question, this inside your arrow function would have the same value as it did right before the arrow function was assigned.

Using the this keyword to itterate through a jquery Selector

Don't use an arrow function. They don't re-bind this.

Instead, the this of the enclosing lexical scope is used.

$("#submit").click(e => {
  e.preventDefault();

  let inputs = $("input");

  inputs.each(function(){
    console.log($(this).val());
  });
});

Should work just fine.

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More information on arrow functions and the behaviour of this:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

How to get the element from a jQuery on() event using an ES6 arrow function?

You can use event.currentTarget to refer to the target element of the handler

$(document).on('click', '.inserted-el', function(event) {

  snippet.log('old -> ' + this.innerHTML + ':' + event.currentTarget.innerHTML);

});

$(document).on('click', '.inserted-el', (event) => {

  snippet.log('new -> ' + this.innerHTML + ':' + event.currentTarget.innerHTML);

});

<!-- Provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->

<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<button class="inserted-el">1</button>

<button class="inserted-el">2</button>

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