How to access custom attributes from event object in React?

Question

React is able to render custom attributes as described at http://facebook.github.io/react/docs/jsx-gotchas.html:

If you want to use a custom attribute, you should prefix it with data-.

<div data-custom-attribute="foo" />

And that's great news except I can't find a way to access it from the event object e.g.:

render: function() { ... <a data-tag={i} style={showStyle} onClick={this.removeTag}></a> ... removeTag: function(event) {     this.setState({inputVal: event.target????});  }, 

The element and data- property render in html fine. Standard properties like style can be accessed as event.target.style fine. Instead of event.target I tried:

 event.target.props.data.tag  event.target.props.data["tag"]  event.target.props["data-tag"]    event.target.data.tag  event.target.data["tag"]  event.target["data-tag"] 

none of these worked.

Answer 1

event.target gives you the native DOM node, then you need to use the regular DOM APIs to access attributes. Here are docs on how to do that:Using data attributes.

You can do either event.target.dataset.tag or event.target.getAttribute('data-tag'); either one works.

Answer 2

To help you get the desired outcome in perhaps a different way than you asked:

render: function() {     ...     <a data-tag={i} style={showStyle} onClick={this.removeTag.bind(null, i)}></a>     ... }, removeTag: function(i) {     // do whatever }, 

Notice the bind(). Because this is all javascript, you can do handy things like that. We no longer need to attach data to DOM nodes in order to keep track of them.

IMO this is much cleaner than relying on DOM events.

Update April 2017: These days I would write onClick={() => this.removeTag(i)} instead of .bind