jQuery expression with parameter

HTML

<div class="test2 test1"></div>

JavaScript

$.expr[':'].hasClassStartingWith = function(el, i, selector) {
  var re = new RegExp("\\b" + selector[3]);
  return re.test(el.className);
}
      
console.log($("div:hasClassStartingWith('te')"));
console.log($("div:hasClassStartingWith('test1')"));
console.log($("div:hasClassStartingWith('test2')"));
console.log($("div:hasClassStartingWith('test3')"));