replace a 2-part class value by 1 part?

replace a 2-part class value by 1 part?

Assume I have a source code like

<div ...... class="aaa bbb" ....>....</div>

How can I replace the class value by another one resp. more precisely how can I delete the "bbb" class?


The final code should look like:

<div ...... class="aaa" ....>....</div>