TypeError：elem.addEventListener不是一个函数

Question

At some place I have a code elem.addEventListener(event, listener, false);

The above code works for

this.buttonBar = doc.getElementsByClassName("wmd-button-bar" + postfix)[0]

But when I change to

this.buttonBar = $('.wmd-button-bar').first();

It does not work. In whole html code I have only one wmd-button-bar class.

Answer 1

The reason why it's not working is because $('.wmd-button-bar').first(); (which equals to $('.wmd-button-bar').eq(0) ) returns the first jQuery wrapped instance.

Therefore you should use jQuery's own API for adding the listener.

However, if you want to receive a first DOM element from collection, you should use

$('.wmd-button-bar').get(0);

This will return first element from the jQuery wrapped collection as a DOM element.