$.get();
$.post();
$.getJSON();

$('div').css();
$('ul').find('li');

$('li').each(callback);
$.each(lis,callback);

function A(){
}
A.prototype.fun_p=function(){console.log("prototpye");};
A.fun_c=function(){console.log("constructor");};
var a=new A();
A.fun_p();//A.fun_p is not a function
A.fun_c();//constructor
a.fun_p();//prototpye
a.fun_c();//a.fun_c is not a function

function A(){
    this.fun_f=function(){
        console.log("Iam in the constructor");
    };
}
A.prototype.fun_p=function(){
    console.log("Iam in the prototype");
};
var a=new A();
a.fun_f();//Iam in the constructor
a.fun_i=function(){
    console.log("Iam in the instance");
};
a.fun_i();//Iam in the instance
a.fun_p();//Iam in the prototype

jQuery.extend = jQuery.fn.extend = function() {
    var options,name, src, copy, copyIsArray, clone,
        target= arguments[0] || {},
        i =1,
        length= arguments.length,
        deep= false;
    // Handle adeep copy situation
    if ( typeoftarget === "boolean" ) {
        deep= target;
        //Skip the boolean and the target
        target= arguments[ i ] || {};
        i++;
    }
    // Handlecase when target is a string or something (possible in deep copy)
    if ( typeoftarget !== "object" && !jQuery.isFunction(target) ) {
        target= {};
    }
    // ExtendjQuery itself if only one argument is passed
    if ( i ===length ) {
        target= this;
        i--;
    }
    for ( ; i< length; i++ ) {
        //Only deal with non-null/undefined values
        if ((options = arguments[ i ]) != null ) {
            //Extend the base object
            for( name in options ) {
                src= target[ name ];
                copy= options[ name ];
                //Prevent never-ending loop
                if( target === copy ) {
                   continue;
                }
                //Recurse if we're merging plain objects or arrays
                if( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray= jQuery.isArray(copy)) ) ) {
                   if( copyIsArray ) {
                       copyIsArray= false;
                       clone= src && jQuery.isArray(src) ? src : [];
                   }else {
                       clone= src && jQuery.isPlainObject(src) ? src : {};
                   }
                   //Never move original objects, clone them
                   target[name ] = jQuery.extend( deep, clone, copy );
                //Don't bring in undefined values
                }else if ( copy !== undefined ) {
                   target[name ] = copy;
                }
            }
        }
    }
    // Returnthe modified object
    return target;
};

var a={};
$.extend(a,{name:"hello"},{age:10});
console.log(a);//Object{name: "hello", age: 10}

var a={};
varb={name:"hello"};
$.extend(a,b);
console.log(a);//Object{name: "hello"}
a.name="hi";
console.log(b);//Object{name: "hello"}

var a={};
varb={name:{age:10}};
$.extend(a,b);
console.log(a.name);//Object{age: 10}
a.name.age=20;
console.log(b.name);//Object{age: 20}

var a={};
varb={name:{age:10}};
$.extend(true,a,b);
console.log(a.name);//Object{age: 10}
a.name.age=20;
console.log(b.name);//Object{age: 10}

var a={name:{job:"Web Develop"}};
var b={name:{age:10}};
$.extend(true,a,b);
console.log(a.name);//age: 10 job: "Web Develop"
//b.name没有覆盖a.name.job。