jQuery中的100个技巧（译）

        <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>

        <script>

            // Different ways to achieve the Document Ready event

            // With jQuery
            $(document).ready(function(){ /* ... */});

            // Short jQuery
            $(function(){ /* ... */});

            // Without jQuery (doesn‘t work in older IE versions)
            document.addEventListener(‘DOMContentLoaded‘,function(){
                // Your code goes here
            });

            // The Trickshot (works everywhere):

            r(function(){
                alert(‘DOM Ready!‘);
            })

            function r(f){/in/.test(document.readyState)?setTimeout(‘r(‘+f+‘)‘,9):f()}

        </script>

        <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>

        <script>

            var route = {
                _routes : {},    // The routes will be stored here

                add    : function(url, action){
                    this._routes[url] = action;
                },

                run : function(){
                    jQuery.each(this._routes, function(pattern){
                        if(location.href.match(pattern)){
                            // "this" points to the function to be executed
                            this();
                        }
                    });
                }
            }

            // Will execute only on this page:
            route.add(‘002.html‘, function(){
                alert(‘Hello there!‘)
            });

            route.add(‘products.html‘, function(){
                alert("this won‘t be executed :(")
            });

            // You can even use regex-es:
            route.add(‘.*.html‘, function(){
                alert(‘This is using a regex!‘)
            });

            route.run();

        </script>

// Instead of writing this:
if($(‘#elem‘).length){
    // do something
}

// You can write this:

$(‘#elem‘).length && log("doing something");

// First, cache the element into a variable:
var elem = $(‘#elem‘);

// Is this a div?
elem.is(‘div‘) && log("it‘s a div");

// Does it have the bigbox class?
elem.is(‘.bigbox‘) && log("it has the bigbox class!");

// Is it visible? (we are hiding it in this example)
elem.is(‘:not(:visible)‘) && log("it is hidden!");

// Animating
elem.animate({‘width‘:200},1);

// is it animated?
elem.is(‘:animated‘) && log("it is animated!");

// How many elements does your page have?
log(‘This page has ‘ + $(‘*‘).length + ‘ elements!‘);

/ Old way
log($(‘#elem‘).length == 1 ? "exists!" : "doesn‘t exist!");

// Trickshot:

jQuery.fn.exists = function(){ return this.length > 0; }

log($(‘#elem‘).exists() ? "exists!" : "doesn‘t exist!");

// Select an element. The second argument is context to limit the search
// You can use a selector, jQuery object or dom element

$(‘li‘,‘#firstList‘).each(function(){
    log($(this).html());
});

log(‘-----‘);

// Create an element. The second argument is an
// object with jQuery methods to be called

var div = $(‘<div>‘,{
    "class": "bigBlue",
    "css": {
        "background-color":"purple"
    },
    "width" : 20,
    "height": 20,
    "animate" : {   // You can use any jQuery method as a property!
        "width": 200,
        "height":50
    }
});

div.appendTo(‘#result‘);

<ul id="links"> 
   <li><a href="007.html">The previous tip</a></li> 
   <li><a href="./009.html">The next tip</a></li>
   <li><a href="http://www.google.com/">Google</a></li> 
</ul>

// Loop through all the links
$(‘#links a‘).each(function(){

    if(this.hostname != location.hostname){
        // The link is external
        $(this).append(‘<img src="assets/img/external.png" />‘)
               .attr(‘target‘,‘_blank‘);
    }

});

<ul id="meals"> <li> <ul class="breakfast"> <li class="eggs">No</li> <li class="toast">No</li> <li class="juice">No</li> </ul> </li> </ul>
// Here is how it is used:

var breakfast = $(‘#meals .breakfast‘);

breakfast.find(‘.eggs‘).text(‘Yes‘)
                      .end() // back to breakfast
                      .find(‘.toast‘).text(‘Yes‘)
                      .end()
                      .find(‘.juice‘).toggleClass(‘juice coffee‘).text(‘Yes‘);

breakfast.find(‘li‘).each(function(){
    log(this.className + ‘: ‘ + this.textContent)
});

        <script>
            // Prevent right clicking on this page
            $(function(){
                $(document).on("contextmenu",function(e){
                    e.preventDefault();
                });
            });
        </script>

// Here is how it is used:

if(window != window.top){
    window.top.location = window.location;
}
else{
    alert(‘This page is not displayed in a frame. Open 011.html to see it in action.‘);
}

// Make the stylesheet visible and editable
$(‘#regular-style-block‘).css({‘display‘:‘block‘, ‘white-space‘:‘pre‘})
                         .attr(‘contentEditable‘,true);

<p class="descr">In certain situations you might want to prevent text on the page from being selectable. Try selecting this text and hit view source to see how it is done.</p>

     <script>
            // Prevent text from being selected
            $(function(){
                $(‘p.descr‘).attr(‘unselectable‘, ‘on‘)
                           .css(‘user-select‘, ‘none‘)
                           .on(‘selectstart‘, false);
          });
     </script>

        <!-- Case 1 - requesting jQuery from the official CDN -->
        <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>

        <!-- Case 2 - requesting jQuery from Google‘s CDN (notice the protocol) -->
        <!-- <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script> -->

        <!-- Case 3 - requesting the latest minor 1.8.x version (only cached for an hour) -->
        <!-- <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10/jquery.min.js"></script> -->

        <!-- Case 4 - requesting the absolute latest jQuery version (use with caution) -->
        <!-- <script src="http://code.jquery.com/jquery.min.js"></script> -->

CODE
// Bad
//var elem = $(‘#elem‘);
//for(var i = 0; i < 100; i++){
//    elem.append(‘<li>element ‘+i+‘</li>‘);
//}

// Good
var elem = $(‘#elem‘),
    arr = [];

for(var i = 0; i < 100; i++){
    arr.push(‘<li>element ‘+i+‘</li>‘);
}

elem.append(arr.join(‘‘));

// You want to parse this address into parts:
var url = ‘http://tutorialzine.com/books/jquery-trickshots?trick=12#comments‘;

// The trickshot:
var a = $(‘<a>‘,{ href: url });

log(‘Host name: ‘ + a.prop(‘hostname‘));
log(‘Path: ‘ + a.prop(‘pathname‘));
log(‘Query: ‘ + a.prop(‘search‘));
log(‘Protocol: ‘ + a.prop(‘protocol‘));
log(‘Hash: ‘ + a.prop(‘hash‘));

// Print the IDs of all LI items
$(‘#colors li‘).each(function(){

    // Access the ID directly, instead
    // of using jQuery‘s $(this).attr(‘id‘)

    log(this.id);

});

// Let‘s try some benchmarks!

var iterations = 10000, i;

timer(‘Fancy‘);

for(i=0; i < iterations; i++){
    // This falls back to a SLOW JavaScript dom traversal
    $(‘#peanutButter div:first‘);
}

timer_result(‘Fancy‘);


timer(‘Parent-child‘);

for(i=0; i < iterations; i++){
    // Better, but still slow
    $(‘#peanutButter div‘);
}

timer_result(‘Parent-child‘);


timer(‘Parent-child by class‘);

for(i=0; i < iterations; i++){
    // Some browsers are a bit faster on this one
    $(‘#peanutButter .jellyTime‘)

// Bad:
// $(‘#pancakes li‘).eq(0).remove();
// $(‘#pancakes li‘).eq(1).remove();
// $(‘#pancakes li‘).eq(2).remove();

// Good:
var pancakes = $(‘#pancakes li‘);

pancakes.eq(0).remove();
pancakes.eq(1).remove();
pancakes.eq(2).remove();

// Alternatively:
// pancakes.eq(0).remove().end()
//           .eq(1).remove().end()
//           .eq(2).remove().end();

$(document).ready(function(){
    function showMenu(){
        alert(‘Showing menu!‘);
        // Doing something complex here
    }

    $(‘#menuButton‘).click(showMenu);
    $(‘#menuLink‘).click(showMenu);

});

var arr = $(‘li‘),
    iterations = 100000;

timer(‘Native Loop‘);

for(var z=0;z<iterations;z++){

    var length = arr.length;
    for(var i=0; i < length; i++){
      arr[i];
    }
}
timer_result(‘Native Loop‘);

timer(‘jQuery Each‘);

for(z=0;z<iterations;z++){

    arr.each(function(i, val) {
      this;
    });
}
timer_result(‘jQuery Each‘);

// Modifying in place
var elem = $(‘#elem‘);

timer(‘In place‘);

for(i=0; i < iterations; i++){

    elem.width(Math.round(100*Math.random()));
    elem.height(Math.round(100*Math.random()));

}

timer_result(‘In place‘);

var parent = elem.parent();

// Detaching first
timer(‘Detached‘);

elem.detach();

for(i=0; i < iterations; i++){

    elem.width(Math.round(100*Math.random()));
    elem.height(Math.round(100*Math.random()));

}

elem.appendTo(parent);

timer_result(‘Detached‘);

        <script>

            // jQuery is loaded at this point. We can use
            // event delegation right away to bind events
            // even before $(document).ready:

            $(document).on(‘click‘, ‘#clickMe‘, function(){
                alert(‘Hit view source and see how this is made‘);
            });

            $(document).ready(function(){

                // This is where you would usually bind event handlers,
                // but as we are using delegation, there is no need to.

                // $(‘#clickMe‘).click(function(){ alert(‘Hey!‘); });
            });

            // Note: You should place your script tags at the bottom of the page.
            // I have included them in the head only to demonstrate that we can bind
            // events before document ready and before the elements are created.

        </script>

<ul id="testList">
 <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li> <li>Item</li>
 </ul>

var style = $(‘<style>‘);

// Try commenting out this line, or change the color:
style.text(‘#testList li{ color:red;}‘);

// Placing it before the result section so it affects the elements
style.prependTo(‘#result‘);

$(document).ready(function(){
    $(‘html‘).addClass(‘JS‘);
});


  html.JS #message { display:block; }
 #message {display:none;}

<ul id="testList"> <li>Old</li> <li>Old</li> <li>Old</li> <li>Old</li> </ul>

var list = $(‘#testList‘);

// Binding an event on the list, but listening for events on the li items:
list.on(‘click‘,‘li‘,function(){
    $(this).remove();
});


// This allows us to create li elements at a later time,
// while keeping the functionality in the event listener

list.append(‘<li>New item (click me!)</li>‘);

<button id="press">Press me!</ul>
var press = $(‘#press‘);

// There is a method that does exactly that, the one():
press.one(‘click‘,function(){
    alert(‘This alert will pop up only once‘);
});

// What this method does, is call on() behind the scenes,
// with a 1 as the last argument:
// press.on(‘click‘,null,null,function(){alert(‘I am the one and only!‘);}, 1);

<button id="press">Press me!</ul>
var press = $(‘#press‘);

// Just a regular event listener:
press.on(‘click‘,function(e, how){
    how = how || ‘‘;
    alert(‘The buton was clicked ‘ + how + ‘!‘);
});

// Trigger the click event
press.trigger(‘click‘);

// Trigger it with an argument
press.trigger(‘click‘,[‘fast‘]);

// Define some variables
var ball = $(‘<div id="ball"></div>‘).appendTo(‘body‘),
startPosition = {}, elementPosition = {};

// Listen for mouse and touch events
ball.on(‘mousedown touchstart‘,function(e){
    e.preventDefault();

    // Normalizing the touch event object
    e = (e.originalEvent.touches) ? e.originalEvent.touches[0] : e;

    // Recording current positions
    startPosition = {x: e.pageX, y: e.pageY};
    elementPosition = {x: ball.offset().left, y: ball.offset().top};

    // These event listeners will be removed later
    ball.on(‘mousemove.rem touchmove.rem‘,function(e){
        e = (e.originalEvent.touches) ? e.originalEvent.touches[0] : e;

        ball.css({
            top:elementPosition.y + (e.pageY - startPosition.y),
            left: elementPosition.x + (e.pageX - startPosition.x),
        });

    });
});

ball.on(‘mouseup touchend‘,function(){
    // Removing the heavy *move listeners
    ball.off(‘.rem‘);
});

<div id="holder"> <button id="button1">1</button> <button id="button2">2</button> <button id="button3">3</button> <button id="button4">4</button> <button id="clear" style="float: right;">Clear</button> </div>


// Lets cache some selectors

var button1 = $(‘#button1‘),
    button2 = $(‘#button2‘),
    button3 = $(‘#button3‘),
    button4 = $(‘#button4‘),
    clear = $(‘#clear‘),
    holder = $(‘#holder‘);

// Case 1: Direct event handling
button1.on(‘click‘,function(){
    log(‘Click‘);
});

// Case 2: Direct event handling of multiple events
button2.on(‘mouseenter mouseleave‘,function(){
    log(‘In/Out‘);
});

// Case 3: Data passing
button3.on(‘click‘, Math.round(Math.random()*20), function(e){

    // This will print the same number over and over again,
    // as the random number above is generated only once:
    log(‘Random number: ‘ + e.data);

});

// Case 4: Events with a namespace
button4.on(‘click.temp‘, function(e){
    log(‘Temp event!‘);
});

button2.on(‘click.temp‘, function(e){
    log(‘Temp event!‘);
});

// Case 5: Using event delegation
$(‘#holder‘).on(‘click‘, ‘#clear‘, function(){
    log.clear();
});

// Case 6: Passing an event map
var t; // timer

clear.on({

    ‘mousedown‘:function(){

        t = new Date();

    },

    ‘mouseup‘:function(){

        if(new Date() - t &gt; 1000){

            // The button has been held pressed
            // for more than a second. Turn off
            // the temp events

            $(‘button‘).off(‘.temp‘);
            alert(‘The .temp events were cleared!‘);
        }

    }
});

<a href="http://google.com/" id="goToGoogle">Go To Google</a>

$(‘#goToGoogle‘).click(false);

<button id="press">点击</button>
 <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>
 <script>

var press = $(‘#press‘);
press.on(‘click‘,function(){
    return ‘Hip‘;
});

// The second event listener has access
// to what was returned from the first

press.on(‘click‘,function(e){
    console.log(e.result + ‘ Hop!‘);
});
 </script>

<button id="button1">Jump</button> <button id="button2">Punch</button> <button id="button3">Click</button> <button id="clear" style="float: right;">Clear</button> <div id="eventDiv"></div>
     <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>




     <script>

var button1 = $(‘#button1‘),
    button2 = $(‘#button2‘),
    button3 = $(‘#button3‘),
    clear = $(‘#clear‘),
    div = $(‘#eventDiv‘);

div.on({
    jump : function(){
        alert(‘Jumped!‘);
    },

    punch : function(e,data){
        alert(‘Punched ‘+data+‘!‘);
    },

    click : function(){
        alert(‘Simulated click!‘);
    }

});

button1.click(function(){
    div.trigger(‘jump‘);
});

button2.click(function(){
    // Pass data along with the event
    div.trigger(‘punch‘,[‘hard‘]);
});

button3.click(function(){
    div.trigger(‘click‘);
});

clear.click(function(){
    //some clear code
});

     </script>

<a href="001.html" class="fetchSize">First Trickshot</a> <br /> 
<a href="034.html" class="fetchSize">This Trickshot</a> <br /> 
<a href="assets/img/ball.png" class="fetchSize">Ball.png</a> <br />

// Loop all .fetchSize links
$(‘a.fetchSize‘).each(function(){

    // Issue an AJAX HEAD request for each one
    var link = this;

    $.ajax({
        type        : ‘HEAD‘,
        url            : link.href,
        complete    : function(xhr){

            // Append the filesize to each
            $(link).append(‘ (‘ + humanize(xhr.getResponseHeader(‘Content-Length‘)) + ‘)‘);

        }
    });

});


function humanize(size){
    var units = [‘bytes‘,‘KB‘,‘MB‘,‘GB‘,‘TB‘,‘PB‘];

    var ord = Math.floor( Math.log(size) / Math.log(1024) );
    ord = Math.min( Math.max(0,ord), units.length-1);

    var s = Math.round((size / Math.pow(1024,ord))*100)/100;
    return s + ‘ ‘ + units[ord];
}

// This is equivalent to passing a callback as the
// second argument (executed on success):

$.get(‘assets/misc/1.json‘).done(function(r){
    log(r.message);
});

// Requesting a file that does not exist. This will trigger
// the failure response. To handle it, you would normally have to
// use the full $.ajax method and pass it as a failure callback,
// but with deferreds you can can simply use the fail method:

$.get(‘assets/misc/non-existing.json‘).fail(function(r){
    log(‘Oops! The second ajax request was "‘ + r.statusText + ‘" (error ‘ + r.status + ‘)!‘);
});

// The trick is in the $.when() function:

$.when($.get(‘assets/misc/1.json‘), $.get(‘assets/misc/2.json‘)).then(function(r1, r2){
    log(r1[0].message + " " + r2[0].message);
});

$.get(‘http://jsonip.com/‘, function(r){ log(r.ip); });

// For older browsers, which don‘t support CORS
// $.getJSON(‘http://jsonip.com/?callback=?‘, function(r){ log(r.ip); });

<p class="content"></p> <p class="content"></p>

var contentDivs = $(‘.content‘);

// Fetch the contents of a text file:
contentDivs.eq(0).load(‘1.txt‘);

// Fetch the contents of a HTML file, and display a specific element:
contentDivs.eq(1).load(‘1.html #header‘);

<form action="">
First name: <input type="text" name="FirstName" value="Bill" /><br />
Last name: <input type="text" name="LastName" value="Gates" /><br />
</form>

// Turn all form fields into a URL friendly key/value string.
// This can be passed as argument of AJAX requests, or URLs.

$(document).ready(function(){
    console.log($("form").serialize()); // FirstName=Bill&LastName=Gates
});

// You can also encode your own objects with the $.param method:
log($.param({‘pet‘:‘cat‘, ‘name‘:‘snowbell‘}));

// The file input field

var fileInput = $(‘input[type=file]‘),
    button = $(‘#upload‘);

button.on(‘click‘, function(){

    // Access the files property, which holds 
    // an array with the selected files
    
    var files = fileInput.prop(‘files‘);

    // No file was chosen!
    if(files.length == 0) {
        alert(‘Please choose a file to upload!‘);
        return false;
    }
    
    // Create a new FormData object
    
    var fd = new FormData();
    
    fd.append(‘file‘, files[0]);
    
    // Upload the file to assets/php/upload.php. Open that file in a text 
    // editor to get a better idea of how it works.
    
    $.ajax({
        url: ‘./assets/php/upload.php‘,
        data: fd,
        contentType:false,        // This will make the browser use the multipart/formdata encoding, which is required for transferring binary data.
        processData:false,        // jQuery shouldn‘t do any processsing on the data - the browser will handle this when it sees we are passing a formdata object.
        type:‘POST‘,
        success: function(m){
            log(m);
        }
    });
});

CODE
// Fetch the publicly accessible data on Tutorialzine‘s Page
var api = ‘http://graph.facebook.com/Tutorialzine/?callback=?‘,
    holder = $(‘#fbdata‘);


$.getJSON(api, function(r){

    // This will always give the current picture
    holder.append(‘<img src="http://graph.facebook.com/Tutorialzine/picture/?type=large">‘);

    holder.append(‘<p>‘+ r.about +‘</p>‘)
    holder.append(‘<a href="‘+ r.website +‘">‘+ r.website +‘</a>‘);

});

// Request weather data:
var api = ‘http://openweathermap.org/data/2.1/find/name?q=paris,france&callback=?‘;


$.getJSON(api, function(r){
    // This will always give the current picture
    log(r.list[0].name + ‘, ‘ + r.list[0].sys.country);
    log(r.list[0].main);

    // Temperatures are in kelvin, subtract 273.15 to convert to Celsius,
});

<div id="post"></div>
// Define variables
var blog = ‘minimaldesks.tumblr.com‘,
    api  = ‘http://‘ + blog + ‘/api/read/json?callback=?‘,
    post = $(‘#post‘);


$.getJSON(api, function(r){

    log(‘Blog title: ‘ + r.tumblelog.title);
    log(‘Description: ‘ + r.tumblelog.description);

    // If this post has a photo, show it
    if(r.posts[0][‘photo-url-250‘]){
        post.append(‘<img src="‘ + r.posts[0][‘photo-url-250‘] + ‘" />‘);
    }
    else{
        log(‘Latest post: ‘ + r.posts[0][‘regular-title‘]);
    }

});

// Define variables
var ip = ‘119.75.218.70‘, // you can optionally put an ip address here
    api  = ‘http://freegeoip.net/json/‘ + ip + ‘?callback=?‘;


$.getJSON(api, function(r){

    console.log(‘How is the weather in ‘ + r.city + ‘, ‘ + r.country_name + ‘?‘);

}); //How is the weather in Beijing, China?

CODE
// Define variables

var query = ‘select * from data.html.cssselect where url="http://www.chucknorrisfacts.com/chuck-norris-top-50-facts" and css=".field-content a"‘;
var yqlAPI = ‘http://query.yahooapis.com/v1/public/yql?q=‘ + encodeURIComponent(query) + ‘ &format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=?‘;


$.getJSON(yqlAPI, function(r){
    
    log(‘Chuck Norris Facts:‘);
    
    $.each(r.query.results.results.a, function(){
        log(‘----------‘);
        log(this.content);
    });
    
});

CODE
// Create an indicator that would be shown whenever an AJAX request occurs:

var preloader = $(‘<div>‘,{ ‘class‘:‘preloader‘ }).appendTo(‘body‘);
var doc = $(document);

// Show the preloader whenever you are making an AJAX request:

doc.ajaxStart(function(){
    preloader.fadeIn();
});

// Hide it when the ajax request finishes

doc.ajaxComplete(function(){
    // Keep it visible for 0.8 seconds after the request completes
    preloader.delay(800).fadeOut();
});

// It will show automatically every time you do an AJAX request:

$.get(‘assets/misc/1.json‘);

// The simple case. Use this instead of alert():
console.log(‘This is a console message!‘);

// It supports embedding of variables as well:
var a = ‘morning‘, b = ‘Miss‘;
console.log(‘Good %s %s! How are you feeling today?‘, a, b);

// Interactively browse the properties of a method (similar to console.log):
console.dir(window);

// Information message (in webkit it looks like console.log)
console.info(‘Everything is OK‘);

// Warning message
console.warn(‘Something may be wrong‘);

// Error message (will print a stack trace)
console.error(‘Ooops. That was bad.‘);

// Counting things
for(var i = 0; i<20; i++){
    console.count(‘Counter Name‘);
}

// Starts a collapsable group of log messages
console.group("Preflight check");
console.info(‘Fuel is OK‘);
console.info(‘Temperature is normal‘);
console.error(‘Wings are missing‘);
console.groupEnd()

// Timing things
console.time(‘The million-dollar loop‘)

var dollars = 0;

for(var i=0;i<100000; i++){
    dollars+=10;
}

console.timeEnd(‘The million-dollar loop‘);

// Profiling code (it will show up in your console‘s Profile tab)
console.profile(‘My app performance‘);

var arr = [];
$.each([0,1,2,3,4,5,6,7,8,9],function(){
    arr.push(this+1);
});

console.profileEnd(‘My app performance‘);

    <input id="testInput" placeholder="YourName"/>
     <script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>

     <script>
// Define the placeholder plugin

$.fn.placeholder = function(){

    if (‘placeholder‘ in document.createElement(‘input‘)){

        // This browser already supports placeholders.
        // Nothing to do here.
        return this;
    }

    this.each(function(){
        var input = $(this);

        input.on(‘focus‘, function(){

            if(input.val() == input.attr(‘placeholder‘)){

                input.val(‘‘);
            }

        }).on(‘blur‘, function(){

            if(input.val() == ‘‘){
                input.val(input.attr(‘placeholder‘));
            }

        });

        // Show the placeholder on load
        input.trigger(‘blur‘);
    });

    return this;
};

// And here is how to use it:
$(‘#testInput‘).placeholder();

// Isolating a block of code:

(function($){
    
    // Declare a variable. It will only be visible in this block.
    var c = 1;
    
    // Define a simple plugin 
    
    $.fn.count = function(){
        
        // Increment and log the counter
        log(c++);
        
        return this;
    };
    
})(jQuery); 

// The c variable is only visible for the plugin and will keep 
// its value between invocations:

$(document).count();

$(‘body‘).count().count();

// Combine properties (useful in plugins).
// The defaults are passed as the first argument.

var supplied = { height: 400 };

var options = $.extend({
    color    : ‘blue‘,
    width    : 200,
    height    : 150
}, supplied);

log(‘New options:‘, options);

// You can also pass more than one object

log(‘Three parents:‘, $.extend({a:2}, {b:3}, {c:4}) );

log(‘-------‘);


// Cloning objects.
// To clone an object, simply pass an empty one
// as the first argument

var original = {a:123, b:‘#fff‘};
var clone = $.extend({}, original);

log(‘Clone:‘, clone);

log(‘-------‘);


// Extending jQuery.
// You can define plugins with extend

$.extend($.fn, {
    plugin1: function(){
        log(‘Plugin 1‘);
        return this;
    },
    plugin2: function(){
        log(‘Plugin 2‘);
        return this;
    }
});

$(‘body‘).plugin1().plugin2();

log(‘-------‘);

// If you pass only one arguments to $.extend,
// it will add the properties to the jQuery object

$.extend({ dontDoThis : 123});

log($.dontDoThis);

log(‘-------‘);

// Deep cloning.
// If you have nested objects, you will have to
// pass one additional argument to extend:

var obj1 = { a: 1, b: 2, c: {d: 3} };
var obj2 = { c: {e: 4}, f:5};

// This won‘t work
// $.extend(obj1, obj2);

// This will
$.extend(true, obj1,obj2);

log(‘Deep clone:‘, obj1);