TypeScript: Using jquery $(this) in event

Question

HTML:

<div>
<button data-id="3">Click Me</button>
</div>

In classic jQuery I would do:

$("div").on("click","button", test);

function test(){
   alert($(this).data("id"));
}

To get the data-id of the clicked element

In TypeScript (in a class) I use:

class foo { ...
 $("div").on("click", "button", (event) => this.test());

 public test(){
    alert($(this).data("id")); // "undefined"
    console.log($(this));
 }

....
}

Here I don't get the clicked element - $(this) is the instance of the class.

What did I do wrong?

Answer 1

According to Typescript's spec "this" is referring to the instance of class the method belongs to/is called on.

You could use the target attribute of the event object passed to the callback:

class foo {
  public test(evt){
    alert($(evt.target).data("id")); // "undefined"
    console.log($(evt.target));
  }
}

Or event.currentTarget depending on if you want to get the element actually clicked on or the element which captured the event.

Answer 2

Using event.currentTarget worked for me when trying to get a data attribute of what was clicked.

$('.elementID').click(e => this.clickedElement(e));


clickedElement(e: JQueryEventObject) {
    var iWasClickedData = $(this).data('key'); // will not work
    var iwasClickedDataFixed = $(e.currentTarget).data('key'); // will work
}

Answer 3

By using arrow functions (event) => TypeScript is giving you a lexically bound this. (In compiled code a previously captured instance called _this)

If you switch to using vanilla function syntax you should be able to use $(this) as you would normally:

$("div").on("click", "button", function(event) { this.test()});

Obviously you have an issue with the instance of the test method being called but I thought it worth sharing.