Extends the jQuery object itself. Can be used to add functions into the jQuery namespace and to [[Plugins/Authoring|add plugin methods]] (plugins). The object that will be merged into the jQuery object Adds two plugin methods.

jQuery.fn.extend({
  check: function() {
    return this.each(function() { this.checked = true; });
  },
  uncheck: function() {
    return this.each(function() { this.checked = false; });
  }
});
$("input[@type=checkbox]").check();
$("input[@type=radio]").uncheck();

Adds two functions into the jQuery namespace

jQuery.extend({
  min: function(a, b) { return a < b ? a : b; },
  max: function(a, b) { return a > b ? a : b; }
});

Extend one object with one or more others, returning the original, modified, object. This is a great utility for simple inheritance. The object to extend The object that will be merged into the first. (optional) More objects to merge into the first Merge settings and options, modifying settings

var settings = { validate: false, limit: 5, name: "foo" };
var options = { validate: true, name: "bar" };
jQuery.extend(settings, options);

settings == { validate: true, limit: 5, name: "bar" } Merge defaults and options, without modifying the defaults

var defaults = { validate: false, limit: 5, name: "foo" };
var options = { validate: true, name: "bar" };
var settings = jQuery.extend({}, defaults, options);

settings == { validate: true, limit: 5, name: "bar" }