Test jQuery

You can only add:

1. new methods on the object
2. new methods on jQuery class objects returned by thejQuery() function
3. pseudo-classes.

Consider the code below. The this.each value represents the jQuery class object, while the this value(same as value) in the callback function code (index,value) represents an HTML element of the list. So $(this) allows to create a jQuery class object(containing only one element, the one represented bythis), on which can be used the .html() method which returns the code HTML of the first item in the list, here this.

jQuery.fn.display= function(){
  this.each(function(index, value){
    alert($(this).html());
  });
};
$("p").display();

The code in answer B allows method chaining.

The code to create a pseudo class that specifies elements that have 5 children(eg for a div: div:five-children) is valid.

jquery.extend(jQuery.expr[":"],
 {
   "five-children": function(element, index, matches, set){
      var nb_child= 0;
      for(var node= element. firstChild; node; node= node. next Sibiling){
        if(node. nodeType== 1){
          nb_child++;
        }
      }
      if(nb_child== 5){
        return true;
      } else{
        return false;
      }
    }
);