Some of the simplest and most common operations on jQuery objects are those that get or set the value of HTML attributes, CSS styles, element content, or element geometry. This chapter describes those methods. First, however, it is worth making some generalizations about getter and setter methods in jQuery:
Rather than defining a pair of methods, jQuery uses a single method as both getter and setter. If you pass a new value to the method, it sets that value; if you don’t specify a value, it returns the current value.
When used as setters, these methods set values on every element in the jQuery object and then return the jQuery object to allow method chaining.
When used as a getter, these methods query only the first
element of the set of elements and return a single value. (Use
map() if you want to query all
elements.) Since getters do not return the jQuery object they are
invoked on, they can only appear at the end of a method chain.
When used as setters, these methods often accept object arguments. In this case, each property of the object specifies a name and a value to be set.
When used as setters, these methods often accept functions as
values. In this case, the function is invoked to compute the value to
be set. The element that the value is being computed for is the
this value: the element index is
passed as the first argument to the function, and the current value is
passed as the second argument.
Keep these generalizations about getters ...