The $.extend method in jquery extends JSON objects and merges to facilitate the invocation of object methods

The $.extend method extends the JSON object by extending an object with one or more other objects, returning the extended object.

Example One

Merge settings and options, modify and return settings

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

Result settings = = {Validate:true, limit:5, Name: "Bar"}

Example Two

Merge defaults and options without modifying the defaults.
var empty = {};
var defaults = {Validate:false, limit:5, Name: "foo"};
var options = {validate:true, name: "Bar"};
var settings = jquery.extend (empty, defaults, options);

Results
Settings = = {Validate:true, limit:5, Name: "Bar"}
Empty = = {Validate:true, limit:5, Name: "Bar"}

Go from the jquery help document

The $.extend method in jquery extends JSON objects and merges to facilitate the invocation of object methods