HTML Data Attributes Older browsers support
Example
Data attributes were introduced in HTML5 which is supported by all modern browsers, but older browsers before HTML5 don't recognize the data attributes.
However, in HTML specifications, attributes that are not recognized by the browser must be left alone and the browser will simply ignore them when rendering the page.
Web developers have utilized this fact to create non-standard attributes which are any attributes not part of the HTML specifications. For example, the value attribute in the line bellow is considered a non-standard attribute because the specifications for the <img> tag don't have a value attribute and it is not a global attribute:
<img src="sample.jpg" value="test" />
This means that although data attributes are not supported in older browsers, they still work and you can set and retrieve them using the same generic JavaScript setAttribute and getAttribute methods, but you cannot use the new dataset property which is only supported in modern browsers.
