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JavaScript

Posted by Joshua Kaufman
Joshua Kaufman
19,193 Points

Arrow Function Syntax doesn't seem to correspond with the "this" element. Why is this?

This Jquery Works fine:

//Task: Prevent spoilerphobes from seeing spoilers //Solution: Hide spoilers and reveal them through user interaction

//1. Hide spoiler $(".spoiler span").hide(); //2. Add a button $(".spoiler").append("<button>Reveal Spoiler!</button>"); //3. When button Pressed $("button").click(function() { //3.1 Show spoiler $(this).prev().show();
//3.2 Get rid of button $(this).hide(); });

But this Jquery does NOT:

//Task: Prevent spoilerphobes from seeing spoilers //Solution: Hide spoilers and reveal them through user interaction

//1. Hide spoiler $(".spoiler span").hide(); //2. Add a button $(".spoiler").append("<button>Reveal Spoiler!</button>"); //3. When button Pressed $("button").click(() => { //3.1 Show spoiler $(this).prev().show();
//3.2 Get rid of button $(this).hide(); });

The second one doesn't really read the command "this", which is weird because I thought "function(){}" === "() => {}" in terms of logic, but evidently it's not the case. Is this a common issue?

1 Answer

Steven Parker
Steven Parker
231,198 Points
Steven Parker
Steven Parker
231,198 Points

That's an intentional part of the arrow function design.

There are programming patterns where the binding of this can be more of an annoyance that a benefit, and this is one of several intentional differences between conventional functions and "arrow" functions. For a complete discussion of the differences, see this Arrow Functions documentation page.

But you can still use them for event handlers, just be sure to pass in the event object, and use its target property instead of this.

Also, to keep your posted code readable, always use the instructions for code formatting in the Markdown Cheatsheet pop-up below the "Add an Answer" area. :arrow_heading_down: