在一个require'd文件中扩展Node.js中的Array.prototype

时间:2011-04-21 05:00:00

标签: javascript node.js require

我在test.js中保存了以下内容。它成功地在浏览器中扩展了Array,但它似乎不适用于node和require。有人可以解释这里有什么问题吗?

(function() {

Array.prototype.max = function() {
  return console.log("Array.prototype.max");
};
return Array.max = function() {
  return console.log("Array.max");
};

}).call(this);

然后,从终端:

> My-MacBook-Pro: me$ node
> var test = require("./test")
> [1,2,3].max()
TypeError: Object 1,2,3 has no method 'max'
    at [object Context]:1:9
    at Interface.<anonymous> (repl.js:171:22)
    at Interface.emit (events.js:64:17)
    at Interface._onLine (readline.js:153:10)
    at Interface._line (readline.js:408:8)
    at Interface._ttyWrite (readline.js:585:14)
    at ReadStream.<anonymous> (readline.js:73:12)
    at ReadStream.emit (events.js:81:20)
    at ReadStream._emitKey (tty_posix.js:307:10)
    at ReadStream.onData (tty_posix.js:70:12)
> Array.max()
TypeError: Object function Array() { [native code] } has no method 'max'
    at [object Context]:1:7
    at Interface.<anonymous> (repl.js:171:22)
    at Interface.emit (events.js:64:17)
    at Interface._onLine (readline.js:153:10)
    at Interface._line (readline.js:408:8)
    at Interface._ttyWrite (readline.js:585:14)
    at ReadStream.<anonymous> (readline.js:73:12)
    at ReadStream.emit (events.js:81:20)
    at ReadStream._emitKey (tty_posix.js:307:10)
    at ReadStream.onData (tty_posix.js:70:12)

2 个答案:

答案 0 :(得分:5)

您可以创建包含扩展程序的文件:

array.extensions.js

if(!Array.prototype.Last){
    Array.prototype.Last = function(){
        return this.slice(-1)[0];
    }
}

if(!Array.prototype.First){
    Array.prototype.First = function(){
        return this[0];
    }
}

然后将此文件包含在您的启动文件中。

app.js:

require('{path}/array.extensions');
var express = require('express');
/* rest of your code */

在启动时引用此文件一次就足以使用......

答案 1 :(得分:0)

REPL中的每个命令都通过vm.runInContext使用共享上下文对象执行。通过复制global对象中的所有内容,在REPL初始化时创建此对象。由于require'd模块只会在之后将Array.prototype 扩展为已复制到上下文对象,因此修改后的版本永远不会公开。

或者至少我可以从the source code推断出来。我对V8的内部工作原理一无所知:)正如你现在可能已经发现的那样,你的例子在REPL之外工作正常。