使用Microsoft ClearScript封装xkpasswd时遇'main is not defined'错误求助

背景 #

我要给xkpasswd的JS库做.NET封装，用Microsoft ClearScript实现。已经解决了第一个问题：执行generate.js时的require is not defined错误，通过设置执行文档为CommonJS模块类别，移除原代码里的Node.js fs、path模块解决。但现在调用时，获取main函数提示main is not defined，尝试获取module.exports也提示module is not defined。

修改后的generate.js代码（关键部分） #

// 移除了fs、path模块的引用
var defaultWordList = require('./xkpasswd-words.json');

// 辅助函数h的定义...（省略原有辅助函数代码）

// 简化readCustomWordList，去掉外部文件读取功能
h.readCustomWordList = function readCustomWordList(input) {
    var rtn = [];
    if (!input) return rtn;
    
    var data = Array.isArray(input) ? input : input.split(',').map(word => word.trim());
    
    data.forEach(word => {
        var trimmed = word.trim();
        if (trimmed.length) rtn.push(trimmed);
    });
    return rtn;
};

module.exports = function main(opts) {
    var o = h.processOpts(opts || {});
    var pattern = o.pattern.split('');
    var uppercase = (typeof o.transform === 'string' && o.transform.toLowerCase() === 'uppercase');
    var password = [];

    var wordList = defaultWordList;
    var customWordList = h.readCustomWordList(o.wordList);

    if (Array.isArray(customWordList) && customWordList.length) {
        wordList = customWordList;
    }

    pattern.forEach(function generatePasswordSegment(type) {
        var value;
        if (type === 'd') value = h.random(0, 9);
        if (type === 's') value = o.separator;
        if (type === 'w' || type === 'W') {
            value = h.getRandomWord(wordList);
            if (typeof o.transform === 'string' && o.transform.toLowerCase() === 'alternate') {
                uppercase = !uppercase;
            }
            if (uppercase || type === 'W') {
                value = value.toUpperCase();
            } else {
                value = value.toLowerCase();
            }
        }
        password.push(value);
    });
    return password.join('');
};

当前.NET调用代码 #

Using engine As New V8ScriptEngine("xkpasswd_engine", V8ScriptEngineFlags.None)
    engine.ExecuteDocument("\generate.js", ModuleCategory.CommonJS)

    Dim mainFunction As ScriptObject =
        DirectCast(engine.Evaluate("main"), ScriptObject)

    Dim opts As Object = New With {
        .complexity = 3,
        .separators = "#.-=+_",
        .pattern = "wswswsdd",
        .transform = "lowercase",
        .wordList = Nothing
    }

    Dim password As String =
        CStr(mainFunction.Invoke(asConstructor:=False, opts))

    Console.WriteLine("Generated password: " & password)
End Using

问题原因 #

ClearScript执行CommonJS模块时，模块内部的module、exports以及定义的main函数都属于模块私有作用域，不会自动暴露到全局，所以直接用engine.Evaluate("main")找不到对应的变量。

修复方案 #

方案1：修改JS代码，把main函数暴露到全局 #

在module.exports = function main(opts) {...}后面添加一行，将main挂载到全局对象：

global.main = main;

修改后，原.NET代码里的engine.Evaluate("main")就能正常获取到函数。

方案2：用ClearScript的Require方法加载模块（推荐） #

不需要修改JS代码，直接在.NET里用Require方法加载模块，获取其导出对象：

Using engine As New V8ScriptEngine("xkpasswd_engine", V8ScriptEngineFlags.None)
    ' 用Require加载模块，返回的就是module.exports对应的函数
    Dim mainFunction As ScriptObject = DirectCast(engine.Require("\generate.js"), ScriptObject)

    Dim opts As Object = New With {
        .complexity = 3,
        .separators = "#.-=+_",
        .pattern = "wswswsdd",
        .transform = "lowercase",
        .wordList = Nothing
    }

    Dim password As String = CStr(mainFunction.Invoke(asConstructor:=False, opts))

    Console.WriteLine("Generated password: " & password)
End Using

这个方案符合CommonJS模块加载规范，不需要改动原JS代码结构。

内容的提问来源于stack exchange，提问作者ElektroStudios