I have learned that HTML5 includes a means to set custom attributes on elements using the data- prefix. However I'm a bit scewered in terms of how to read the properties during a javascript code block. I guess it is my interpretation of how the DOMStringMap is working thats off.
Could someone simplify how to read the properties of the following sample html.
<span data-complex-key="howtoRead" data-id="anId">inner</span>
Trying following doesnt really work as expected
spanEl.dataset['id'] // straight-forward and result is anId
spanEl.dataset['complex-key'] // undefined
spanEl.dataset['complex']['key'] // throws 'cannot read property of undefined'
spanEl.getAttribute('complex-key') // there's a null however,
spanEl.getAttribute('data-complex-key') // this variant seems to work
Another thing that makes me wonder is, the CSS selectors seems to follow the excact same pattern as to which is i written in the DOM, so why is this not the case with reading from javascript.
For instance, this would match
span[data-complex-key="howtoRead"] { color:green }
Appreciate the help, still getting more and more intreaged with the HTML5 Canvas, Video and local Data Storage :)
In vanilla-JS, assuming spanEl
is a reference to the DOM node
spanEl.dataset.complexKey
will work using the camelCase
notation (see http://jsbin.com/oduguw/3/edit ) when your data attribute contains hypens ( -
) and also
spanEl.getAttribute('data-complex-key')
will work fine as you already noticed. As a side note, in jQuery you can access to that data
attribute with
$(spanEl).data("complex-key")
In Chrome, it seems to map the data keys in a not-so-straightforward way:
console.log(spanEl.dataset);
//shows:
//DOMStringMap
// complexKey: "howtoRead"
// id: "anId"
It converts "complex-key" to "complexKey".
While not being completely straightforward, this behavior is defined in the HTML5 spec here:
http://dev.w3.org/html5/spec//global-attributes.html#dom-dataset
Your first and last method are correct while not using any libraries. However a key with a minus sign is converted to Camel Case, so complex-key becomes complexKey:
spanEl.dataset['id']
spanEl.dataset['complexKey']
spanEl.getAttribute('data-complex-key')
However, only the last one works in IE up to 9. (I don't know about 10.) The data attributes are nothing else than normal attributes having a naming convention in this case.
spanEl.dataSet["complexKey"]
//Using jQuery you can try this
$('span').data('complex-key') // Will give you **howtoRead**
$('span').data('id') // Will give you **anId**
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