10个可以直接拿来用的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10段非常实用的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);   
});   

7.使用jQuery和Ajax自动填充选择框

$(function(){   
$("select#ctlJob").change(function(){   
$.getJSON("/select.php",{id: $(this).val(), ajax: 'true'}, function(j){   
var options = '';   
for (var i = 0; i < j.length; i++) {   
options += '   
' + j[i].optionDisplay + '   
';   
}   
$("select#ctlPerson").html(options);   
})   
})   
})   

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;   
  });   
};