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JavaScript Introducing the Practice

Posted by Alina Bylkova
Alina Bylkova
6,862 Points

The keyword 'this' behaves strangely when declared inside arrow function (ES6)

https://w.trhou.se/xbutg4gnu6 (see code in lines 25-27 in the workspace)

When I run the code below, it doesn't work locally unless I replace () => { with function() {. On the other hand this code works partially in Treehouse Workspace - it appliesstrike property, but it doesn't remove it on the second double click (meaning toggle doesn't work):

$('ul').on('dblclick', 'li', () => { $(this).toggleClass('strike'); });

1 Answer

Steven Parker
Steven Parker
231,261 Points
Steven Parker
Steven Parker
231,261 Points

Arrow functions are not exact replacements for conventional functions. One difference is that they do not establish a value for "this".

For event handlers, you can usually use the "target" property of the passed-in event object as a substitute:

$('ul').on('dblclick', 'li', e => { $(e.target).toggleClass('strike'); });

For more details on arrow functions and how they are different from conventional functions, see this MDN page on Arrow function expressions.