使用React.js获取数据属性

Question

Why do I have to put data-* in every html child attribute so i won't get undefined by clicking on parent ? Ie

<li data-item="item-1">
  <img src="../img" alt="img" />
  <p>Some text</p>
</li>

By this example i will get item-1 whenever i click near the borders of <li> but whenever i click either img or text/paragraph i get undefined . But when I set data-item on <li> childs i get normal data value. What?

PS. The way i get data-* is for example

handleClick(event){
  let data = event.target.dataset['item']
}
...
<li data-item="item-1" onClick={this.handleClick.bind(this)}>...</li>

What am I doing wrong, that I have to put into every <li> child data-* so I won't get undefined on whole <li> block on<Event> ?

Answer 1

FYI, the problem has nothing to do with React. It's how DOM events in browsers work. Have a look at this quirksmode.org article to learn more about how event propagation works.

event.target will always refer to the element the event was triggered on. So if you click on the <p> element, event.target will refer to that element. Since <p> doesn't have a data-* attribute you get undefined .

To always get the element where the handler is bound to (ie the <li> element in your example), use event.currentTarget instead.