可以使用[]而不是。

这允许您查找与变量匹配的属性。

obj = {a:"test"};
var propname = "a";
var b = obj[propname];  // "test"

您还可以使用此命令获取/设置名称不是合法标识符的对象属性。

obj["class"] = "test";  // class is a reserved word; obj.class would be illegal.
obj["two words"] = "test2"; // using dot operator not possible with the space.

有些人不知道这一点，最终像这样使用eval()，这是一个非常糟糕的主意:

var propname = "a";
var a = eval("obj." + propname);

这更难阅读，更难发现错误(不能使用jslint)，执行速度更慢，并可能导致XSS漏洞。

这似乎只适用于Firefox (SpiderMonkey)。函数内部:

Arguments[-2]给出了参数的个数(与Arguments .length相同) Arguments[-3]给出了被调用的函数(与Arguments .callee相同)

令人惊讶的是，很多人都没有意识到它也是面向对象的。

JavaScript中的时间戳:

// Usual Way
var d = new Date();
timestamp = d.getTime();

// Shorter Way
timestamp = (new Date()).getTime();

// Shortest Way
timestamp = +new Date();

这里有一些捷径:

var a = []; // equivalent to new Array()
var o = {}; // equivalent to new Object()

正如Marius已经指出的，可以在函数中使用公共静态变量。

我通常使用它们来创建只执行一次的函数，或者缓存一些复杂的计算结果。

下面是我以前的“单例”方法的例子:

var singleton = function(){ 

  if (typeof arguments.callee.__instance__ == 'undefined') { 

    arguments.callee.__instance__ = new function(){

      //this creates a random private variable.
      //this could be a complicated calculation or DOM traversing that takes long
      //or anything that needs to be "cached"
      var rnd = Math.random();

      //just a "public" function showing the private variable value
      this.smth = function(){ alert('it is an object with a rand num=' + rnd); };

   };

  }

  return arguments.callee.__instance__;

};


var a = new singleton;
var b = new singleton;

a.smth(); 
b.smth();

如您所见，在这两种情况下构造函数都只运行一次。

For example, I used this approach back in 2004 when I had to create a modal dialog box with a gray background that covered the whole page (something like Lightbox). Internet Explorer 5.5 and 6 have the highest stacking context for <select> or <iframe> elements due to their "windowed" nature; so if the page contained select elements, the only way to cover them was to create an iframe and position it "on top" of the page. So the whole script was quite complex and a little bit slow (it used filter: expressions to set opacity for the covering iframe). The "shim" script had only one ".show()" method, which created the shim only once and cached it in the static variable :)