The class method on Html is a helper to render a class attribute similar to Vue.js' :class property.
It expects an array (or a Collection), and will toggle a set of classes depending on the values of the array.
<div {{ html()->class(['foo', 'bar' => true, 'baz' => false]) }}>
<div class="foo bar">
If there's just a value (non-associative), the class will always be added. Otherwise, the class—specified by the array key—will only appear in the list if the value evaluates to true (non-strict).