可以直接拿来用的jQuery代码片段

     jQuery里提供了许多创建交互式网站的方法，在开发Web项目时，开发人员应该好好利用jQuery代码，它们不仅能给网站带来各种动画、特效，还会提高网站的用户体验。

    本文收集了几个非常实用的jQuery代码片段，你可以直接复制黏贴到代码里，但请开发者注意了，要理解代码再使用哦。下面就让我们一起来享受jQuery代码的魅力之处吧。

1.预加载图片

(function($) {  
  var cache = [];  
  // Arguments are image paths relative to the current page.  
  $.preLoadImages = function() {  
    var args_len = arguments.length;  
    for (var i = args_len; i--;) {  
      var cacheImage = document.createElement('img');  
      cacheImage.src = arguments[i];  
      cache.push(cacheImage);  
    }  
  }  
jQuery.preLoadImages("image1.gif", "/path/to/image2.png");  

2. 让页面中的每个元素都适合在移动设备上展示

var scr = document.createElement('script');  
scr.setAttribute('src', 'https://ajax.googleapis.com/ajax/libs/jquery/1.5.2/jquery.min.js');  
document.body.appendChild(scr);  
scr.onload = function(){  
    $('div').attr('class', '').attr('id', '').css({  
        'margin' : 0,  
        'padding' : 0,  
        'width': '100%',  
        'clear':'both'  
    });  
}; 

3.图像等比例缩放

$(window).bind("load", function() {  
    // IMAGE RESIZE  
    $('#product_cat_list img').each(function() {  
        var maxWidth = 120;  
        var maxHeight = 120;  
        var ratio = 0;  
        var width = $(this).width();  
        var height = $(this).height();  
        if(width > maxWidth){  
            ratio = maxWidth / width;  
            $(this).css("width", maxWidth);  
            $(this).css("height", height * ratio);  
            height = height * ratio;  
        }  
        var width = $(this).width();  
        var height = $(this).height();  
        if(height > maxHeight){  
            ratio = maxHeight / height;  
            $(this).css("height", maxHeight);  
            $(this).css("width", width * ratio);  
            width = width * ratio;  
        }  
    });  
    //$("#contentpage img").show();  
    // IMAGE RESIZE  
});  

4.返回页面顶部

// Back To Top  
$(document).ready(function(){   
  $('.top').click(function() {    
     $(document).scrollTo(0,500);    
  });  
});   
//Create a link defined with the class .top  
<a href="#" class="top">Back To Top</a> 

5.使用jQuery打造手风琴式的折叠效果

var accordion = {  
     init: function(){  
           var $container = $('#accordion');  
           $container.find('li:not(:first) .details').hide();  
           $container.find('li:first').addClass('active');  
           $container.on('click','li a',function(e){  
                  e.preventDefault();  
                  var $this = $(this).parents('li');  
                  if($this.hasClass('active')){  
                         if($('.details').is(':visible')) {  
                                $this.find('.details').slideUp();  
                         } else {  
                                $this.find('.details').slideDown();  
                         }  
                  } else {  
                         $container.find('li.active .details').slideUp();  
                         $container.find('li').removeClass('active');  
                         $this.addClass('active');  
                         $this.find('.details').slideDown();  
                  }  
           });  
     }  
}; 

6.通过预加载图片廊中的上一幅下一幅图片来模仿Facebook的图片展示方式

var nextimage = "/images/some-image.jpg";  
$(document).ready(function(){  
window.setTimeout(function(){  
var img = $("").attr("src", nextimage).load(function(){  
//all done  
});  
}, 100);  
});  

8.自动替换丢失的图片

// Safe Snippet  
$("img").error(function () {  
    $(this).unbind("error").attr("src", "missing_image.gif");  
});  
// Persistent Snipper  
$("img").error(function () {  
    $(this).attr("src", "missing_image.gif");  
});  

9.在鼠标悬停时显示淡入/淡出特效

$(document).ready(function(){  
    $(".thumbs img").fadeTo("slow", 0.6); // This sets the opacity of the thumbs to fade down to 60% when the page loads  
    $(".thumbs img").hover(function(){  
        $(this).fadeTo("slow", 1.0); // This should set the opacity to 100% on hover  
    },function(){  
        $(this).fadeTo("slow", 0.6); // This should set the opacity back to 60% on mouseout  
    });  
});  

10.清空表单数据

function clearForm(form) {  
  // iterate over all of the inputs for the form  
  // element that was passed in  
  $(':input', form).each(function() {  
    var type = this.type;  
    var tag = this.tagName.toLowerCase(); // normalize case  
    // it's ok to reset the value attr of text inputs,  
    // password inputs, and textareas  
    if (type == 'text' || type == 'password' || tag == 'textarea')  
      this.value = "";  
    // checkboxes and radios need to have their checked state cleared  
    // but should *not* have their 'value' changed  
    else if (type == 'checkbox' || type == 'radio')  
      this.checked = false;  
    // select elements need to have their 'selectedIndex' property set to -1  
    // (this works for both single and multiple select elements)  
    else if (tag == 'select')  
      this.selectedIndex = -1;  
  });  
}; 

11.预防对表单进行多次提交

$(document).ready(function() {  
  $('form').submit(function() {  
    if(typeof jQuery.data(this, "disabledOnSubmit") == 'undefined') {  
      jQuery.data(this, "disabledOnSubmit", { submited: true });  
      $('input[type=submit], input[type=button]', this).each(function() {  
        $(this).attr("disabled", "disabled");  
      });  
      return true;  
    }  
    else  
    {  
      return false;  
    }  
  });  
});  

14.平衡高度或Div元素

var maxHeight = 0;  
$("div").each(function(){  
   if ($(this).height() > maxHeight) { maxHeight = $(this).height(); }  
});  
$("div").height(maxHeight);  

15. 在窗口滚动时自动加载内容

var loading = false;  
$(window).scroll(function(){  
    if((($(window).scrollTop()+$(window).height())+250)>=$(document).height()){  
        if(loading == false){  
            loading = true;  
            $('#loadingbar').css("display","block");  
            $.get("load.php?start="+$('#loaded_max').val(), function(loaded){  
                $('body').append(loaded);  
                $('#loaded_max').val(parseInt($('#loaded_max').val())+50);  
                $('#loadingbar').css("display","none");  
                loading = false;  
            });  
        }  
    }  
});  
$(document).ready(function() {  
    $('#loaded_max').val(50);  
});  

From：http://www.youkuaiyun.com/article/2013-07-16/2816238-15-jQuery-Code-Snippets-for-Developers