50个JQuery代码技巧让你变成js高手(2)

26. 显示或者删除输入框的缺省值
//This snippet will show you how to keep a default value
//in a text input field for when a user hasn't entered in
//a value to replace it
swap_val = [];
$(".swap").each(function(i){
    swap_val[i] = $(this).val();
    $(this).focusin(function(){
        if ($(this).val() == swap_val[i]) {
            $(this).val("");
        }
    }).focusout(function(){
        if ($.trim($(this).val()) == "") {
            $(this).val(swap_val[i]);
        }
    });
});
<INPUT class=swap value="Enter Username here.." type=text>
27. 指定时间后自动隐藏或者关闭元素(1.4支持）
//Here's how we used to do it in 1.3.2 using setTimeout
setTimeout(function() {
$('.mydiv').hide('blind', {}, 500)
}, 5000);
//And here's how you can do it with 1.4 using the delay() feature (this is a lot like sleep)
$(".mydiv").delay(5000).hide('blind', {}, 500);
28. 动态创建元素到DOM
var newgbin1Div = $('');
newgbin1Div.attr('id','gbin1.com').appendTo('body');
29. 限制textarea的字符数量
jQuery.fn.maxLength = function(max){
this.each(function(){
    var type = this.tagName.toLowerCase();
    var inputType = this.type? this.type.toLowerCase() : null;
    if(type == "input" && inputType == "text" || inputType == "password"){
      //Apply the standard maxLength
      this.maxLength = max;
    }
    else if(type == "textarea"){
      this.onkeypress = function(e){
        var ob = e || event;
        var keyCode = ob.keyCode;
        var hasSelection = document.selection? document.selection.createRange().text.length > 0 : this.selectionStart != this.selectionEnd;
        return !(this.value.length >= max && (keyCode > 50 || keyCode == 32 || keyCode == 0 || keyCode == 13) && !ob.ctrlKey && !ob.altKey && !hasSelection);
      };
      this.onkeyup = function(){
        if(this.value.length > max){
          this.value = this.value.substring(0,max);
        }
      };
    }
});
};
//Usage:
$('#gbin1textarea').maxLength(500);
30. 为函数创建一个基本测试用例
//Separate tests into modules.
module("Module B");
test("some other gbin1.com test", function() {
//Specify how many assertions are expected to run within a test.
expect(2);
//A comparison assertion, equivalent to JUnit's assertEquals.
equals( true, false, "failing test" );
equals( true, true, "passing test" );
});
31. 使用jQuery克隆元素
var cloned = $('#gbin1div').clone();
32. 测试一个元素在jQuery中是否可见
if($(element).is(':visible') == 'true') { //The element is Visible }
33. 元素屏幕居中
jQuery.fn.center = function () {
this.css('position','absolute');
this.css('top', ( $(window).height() - this.height() ) / +$(window).scrollTop() + 'px');
this.css('left', ( $(window).width() - this.width() ) / 2+$(window).scrollLeft() + 'px');return this;
}
//Use the above function as: $('#gbin1div').center();
34. 使用特定名字的元素对应的值生成一个数组
var arrInputValues = new Array();
$("input[name='table[]']").each(function(){
     arrInputValues.push($(this).val());
});
35. 剔除元素中的HTML
(function($) {
    $.fn.stripHtml = function() {
        var regexp = /<("[^"]*"|'[^']*'|[^'">])*>/gi;
        this.each(function() {
            $(this).html(
                $(this).html().replace(regexp,"")
            );
        });
        return $(this);
    }
})(jQuery);
//usage:
$('p').stripHtml();
36. 使用closest来得到父元素
$('#searchBox').closest('div');
37. 使用firebug来记录jQuery事件
// Allows chainable logging
// Usage: $('#someDiv').hide().log('div hidden').addClass('someClass');
jQuery.log = jQuery.fn.log = function (msg) {
      if (console){
         console.log("%s: %o", msg, this);
      }
      return this;
};
38. 点击链接强制弹出新窗口
jQuery('a.popup').live('click', function(){
newwindow=window.open($(this).attr('href'),'','height=200,width=150');
if (window.focus) {newwindow.focus()}
return false;
});
39. 点击链接强制打开新标签页
jQuery('a.newTab').live('click', function(){
newwindow=window.open($(this).href);
jQuery(this).target = "_blank";
return false;
});
40. 使用siblings()来处理同类元素
// Rather than doing this
$('#nav li').click(function(){
    $('#nav li').removeClass('active');
    $(this).addClass('active');
});
// Do this instead
$('#nav li').click(function(){
    $(this).addClass('active')
        .siblings().removeClass('active');
});
41. 选择或者不选页面上全部复选框
var tog = false; // or true if they are checked on load
$('a').click(function() {
    $("input[type=checkbox]").attr("checked",!tog);
    tog = !tog;
});
42. 基于输入文字过滤页面元素
//If the value of the element matches that of the entered text
//it will be returned
$('.gbin1Class').filter(function() {
    return $(this).attr('value') == $('input#gbin1Id').val() ;
})
43. 取得鼠标的X和Y坐标
$(document).mousemove(function(e){
$(document).ready(function() {
$().mousemove(function(e){
$('#XY').html("Gbin1 X Axis : " + e.pageX + " |

补充：web前端 , JavaScript ,