请教各位大侠一个JAVASCRIPT定义方式

如果TB存在，TB=TB否则 TB={};

var TB=TB||{};
这是一个逻辑与操作，当TB真（存在）后面的就不用再执行了，TB就是等于TB了。如果TB为假（可能是undefined，null）时就往下执行，此时TB={}了。

var poro = poro||{};
首先,这里的||是或逻辑,与JAVA相同,如果poro不为null(javascript中undefined与null相同),那么||后面的语句不会执行.
第二,{}在js中相当于new Object()
最后,var poro = poro||{};如果porop被定义过且值不为null那么就将值为其本身,如果没有定义过就new它

[code=JScript]var TB = TB ||
{
}
;
TB.Header = function()
{
      var f = function(v)
      {
            return typeof(v) != "string" ? v : document.getElementById(v)
      }
      ;
      var s = navigator.userAgent.toLowerCase();
      var n = /msie/.test(s) && ! / opera / .test(s);
      var k = n && ! / msie 7 / .test(s) && ! / msie 8 / .test(s);
      var g =
      {
            getCookie : function(w)
            {
                  var v = document.cookie.match("(?:^|;)\\s*" + w + "=([^;]*)");
                  return(v && v[1]) ? decodeURIComponent(v[1]) : ""
            }
            , parseQueryParams : function(B)
            {
                  var y =
                  {
                  }
                  ;
                  var w = B.split("&");
                  for(var z = 0, A = w.length; z < A; ++ z)
                  {
                        var x = w[z], C = x.search("=");
                        var D = x.substring(0, C);
                        var v = x.substring(C + 1, x.length);
                        y[decodeURIComponent(D)] = decodeURIComponent(v)
                  }
                  return y
            }
            , trim : function(v)
            {
                  return v.replace(/^\s+|\s+$/g, "")
            }
            , hasClass : function(w, v)
            {
                  w = f(w);
                  if( ! w || ! v || ! w.className)
                  {
                        return false
                  }
                  return(" " + w.className + " ").indexOf(" " + v + " ") > - 1
            }
            , addClass : function(w, v)
            {
                  w = f(w);
                  if( ! w || ! v)
                  {
                        return
                  }
                  if(this.hasClass(w, v))
                  {
                        return
                  }
                  w.className += " " + v
            }
            , removeClass : function(w, v)
            {
                  w = f(w);
                  if( ! this.hasClass(w, v))
                  {
                        return
                  }
                  w.className = w.className.replace(new RegExp(v, "g"), "");
                  if( ! this.trim(w.className))
                  {
                        w.removeAttribute(n ? "className" : "class")
                  }
            }
            , addEvent : function(x, w, v)
            {
                  x = f(x);
                  if( ! x || ! w || typeof(v) != "function")
                  {
                        return
                  }
                  if(x.addEventListener)
                  {
                        x.addEventListener(w, v, false)
                  }
                  else
                  {
                        if(x.attachEvent)
                        {
                              x.attachEvent("on" + w, v)
                        }
                  }
            }
            , stopEvent : function(v)
            {
                  if(v.stopPropagation)
                  {
                        v.stopPropagation()
                  }
                  else
                  {
                        v.cancelBubble = true
                  }
                  if(v.preventDefault)
                  {
                        v.preventDefault()
                  }
                  else
                  {
                        v.returnValue = false
                  }
            }
            , escapeHTML : function(w)
            {
                  var x = document.createElement("div");
                  var v = document.createTextNode(w);
                  x.appendChild(v);
                  return x.innerHTML
            }
      }
      ;
      var t = g.getCookie("_nk_");
      var i = g.getCookie("uc1");
      var d = g.parseQueryParams(i);
      var p = g.getCookie("_l_g_") && t;
      var o = parseInt(d._msg_) || 0;
      var j = new Date().getTime();
      var c = document.getElementsByTagName("script");
      var q = c[c.length - 1].getAttribute("version") == "co";
      var r = (document.location.href.indexOf("https://") === 0);
      function a(x)
      {
            x = f(x);
            if( ! x)
            {
                  return
            }
            var w = x.children[1];
            if( ! w)
            {
                  return
            }
            if( ! r)
            {
                  var v = document.createElement("iframe");
                  v.src = "about: blank";
                  v.className = "menu-list";
                  v.style.border = "none";
                  x.insertBefore(v, w); x.iframe = v
            }
            x.menulist = w;
            x.onmouseenter = function()
            {
                  g.addClass(this, g.hasClass(this, "forum-v2") ? "forum-hover" : "hover"); if(r)
                  {
                        return
                  }
                  this.iframe.style.height = (parseInt(this.menulist.offsetHeight) - 5) + "px";
                  this.iframe.style.width = this.menulist.offsetWidth
            }
            ;
            x.onmouseleave = function()
            {
                  g.removeClass(this, g.hasClass(this, "forum-v2") ? "forum-hover" : "hover")
            }
      }
      function m(y, x, v)
      {
            var w = document.createElement("option");
            w.innerHTML = y;
            w.value = x;
            w.className = v || "";
            return w
      }
code]

调试易

请教各位大侠一个JAVASCRIPT定义方式

解决方案 »