Contains CSS attribute selector

In CSS you can detect if an attribute contains a value. This is one of many attribute selectors.

You can use this to apply a default value, if say, a utility class that applies a background doesn’t exist, using :not.

/* If this doesn’t have a 'bg-' prefixed class, 
apply a default */
.my-element:not([class*='bg-']) {
  background: #efefef;
}