writing-data-to-the-html-dom-as-data-attribute-1ef9fef.md

Writing Data to the HTML DOM as DATA-* Attribute

OpenUI5 supports writing custom data to the HTML DOM.

These are two use cases, where this feature can be useful:

• To generate markers in the HTML from data binding which then can then be used for data-dependent styling.

• To create stable anchors in the HTML which can be used for automated tests.

A "data-" prefix is added to the key and the result is then written as an attribute into the root HTML element of the control. The CustomData value is written as an attribute value.

For this, the key has to be a valid HTML ID and the value has to be a string; otherwise an error is logged.

Note:

HTML attribute names are case-insensitive and browsers may convert the key to lowercase.

Do not write too much data into the DOM.

In JavaScript, you can set the flag as shown in the following code snippet:

myButton.data("mydata", "Hello", true); // attach some data to the Button and mark it as
          "write to HTML"

To set the writeToDom flag in XML views, the aggregation has to be written in expanded notation:

<Button ... >
  <customData>
  <core:CustomData key="mydata" value="Hello" writeToDom="true" />
  </customData>
</Button>

This results in the following HTML:

<button ...  data-myData="Hello"  ... >

The CSS can now use attribute selectors to check the presence or the value of the custom data attribute:

button[data-mydata="Hello"] { border: 3px solid red !important; }