Rhino 中没有 Array.filter() 吗？

为什么我不能使用Array.filter()在犀牛？

代码是这样的：

var simple_reason = ["a", "b", "c"];
print(typeof simple_reason.filter);

var not_so_simple_reason = new Array("a", "b", "c");
print(typeof not_so_simple_reason.filter);

两种情况都会输出“未定义”。

There is no standardized filter function for Javascript Arrays, it is only an extension to the standard. (There is as of the ES5 spec published just a month after this answer was posted.) The MDC reference page https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/filter gives you an compatibility sample to use for those implementations that do not support it...

if (!Array.prototype.filter)
{
  Array.prototype.filter = function(fun /*, thisp*/)
  {
    var len = this.length >>> 0;
    if (typeof fun != "function")
      throw new TypeError();

    var res = new Array();
    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in this)
      {
        var val = this[i]; // in case fun mutates this
        if (fun.call(thisp, val, i, this))
          res.push(val);
      }
    }

    return res;
  };
}