How to access custom attributes from event object in React?

How to access custom attributes from event object in React?

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-.

And that’s great news except I can’t find a way to access it from the event object e.g.:
render: function() {



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.

Solutions/Answers:

Solution 1:

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.

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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

Solution 2:

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:

https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_data_attributes#JavaScript_Access

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

Solution 3:

Here’s the best way I found:

var attribute = event.target.attributes.getNamedItem('data-tag').value;

Those attributes are stored in a “NamedNodeMap”, which you can access easily with the getNamedItem method.

Solution 4:

Or you can use a closure :

render: function() {
...
<a data-tag={i} style={showStyle} onClick={this.removeTag(i)}></a>
...
},
removeTag: function (i) {
    return function (e) {
    // and you get both `i` and the event `e`
    }.bind(this) //important to bind function 
}

Solution 5:

// Method inside the component
userClick(event){
 let tag = event.currentTarget.dataset.tag;
 console.log(tag); // should return Tagvalue
}
// when render element
<a data-tag="TagValue" onClick={this.userClick}>Click me</a>

Solution 6:

<div className='btn' onClick={(e) =>
     console.log(e.currentTarget.attributes['tag'].value)}
     tag='bold'>
    <i className='fa fa-bold' />
</div>

so e.currentTarget.attributes['tag'].value works for me

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