用nodejs访问ActiveX对象，以操作Access数据库为例。

起因
有人提问“如果用nodejs访问sql server？”
找了找资料，发现有两类解决方法，使用第三方nodejs插件：https://github.com/orenmazor/node-tds、使用ADODB.ConnectionActiveX对象。
参考：
http://stackoverflow.com/questions/857670/how-to-connect-to-sql-server-database-from-javascript
http://stackoverflow.com/questions/4728385/connecting-to-a-remote-microsoft-sql-server-from-node-js
如果用ActiveX那么在Windows下nodejs将会无所不能，类似写asp。那它们怎么通信？得动手试试
经过
思路
用nodejs通过cscript.exe(windows脚本进程)间接访问ActiveX
cscript能解析jscript和vbscript两种脚本，无疑为方便维护选jscript开发。
参考：http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/cscript_overview.mspx?mfr=true
需解决的问题
1、跨进程通信
新版的nodejs里增加了对子进程的操作，跨进程通信不是问题。
http://nodejs.org/docs/latest/api/all.html#child_Processes

var util = require('util'), 
exec = require('child_process').exec, 
child; 
child = exec('cat *.js bad_file | wc -l', 
function (error, stdout, stderr) { 
console.log('stdout: ' + stdout); 
console.log('stderr: ' + stderr); 
if (error !== null) { 
console.log('exec error: ' + error); 
} 
});

如例我们可以拿到控制台的输出内容stdout！

2、数据库访问相关ActiveX，ADODB.Connection
参考：http://msdn.microsoft.com/en-us/library/windows/desktop/aa746471%28v=vs.85%29.aspx

var connection = new ActiveXObject("ADODB.Connection"); 
var result = 'ok'; 
try{ 
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile); 
connection.Execute(params.sql); 
} catch(ex){ 
result = ex.message; 
} 
return { 
result: result 
};

connection.Open(connectionString)，链接字符串参数可以设置访问sql server。
参考：http://www.connectionstrings.com/sql-server-2005
3、为方便维护，特别将cscript和nodejs的脚本合并，用typeof exports判断当前运行环境。
4、字符编码cscript代码使用ascii编码
非ascii码字符进行“\uHHHH”Unicode编码。
5、命令行字符需转义，双引号、百分号在命令行有特殊意义。
参数传递使用base64编码，避免冲突
cscript环境MSXML2.DOMDocument可以做base64编解码

function base64Decode(base64){ 
var xmldom = new ActiveXObject("MSXML2.DOMDocument"); 
var adostream = new ActiveXObject("ADODB.Stream"); 
var temp = xmldom.createElement("temp"); 
temp.dataType = "bin.base64"; 
temp.text = base64; 
adostream.Charset = "utf-8"; 
adostream.Type = 1; // 1=adTypeBinary 2=adTypeText 
adostream.Open(); 
adostream.Write(temp.nodeTypedValue); 
adostream.Position = 0; 
adostream.Type = 2; // 1=adTypeBinary 2=adTypeText 
var result = adostream.ReadText(-1); // -1=adReadAll 
adostream.Close(); 
adostream = null; 
xmldom = null; 
return result; 
}

总结
调用流程
1、创建子进程，传递经过编码的参数；
2、子进程处理完毕将数据JSON格式化输出到控制台；（子进程自动结束）
3、读取控制台的数据，执行回调函数。

优势
1、使nodejs拥有访问ActiveX对象的能力；
2、实现简单，开发维护方便。

劣势
1、只能运行在Windows平台；
2、数据编解码会消耗更多cpu；
3、每次调用需要创建一个子进程重新连接。(可改进)
总结
1、具有一定实用性；
2、跨进程通信性能可继续探索。
模块代码：

var Access = { 
create: function(params){ 
var fso = new ActiveXObject("Scripting.FileSystemObject"); 
var result = 'ok'; 
if (!fso.FileExists(params.accessfile)){ 
var adoxcatalog = new ActiveXObject("ADOX.Catalog"); 
try { 
adoxcatalog.Create("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile); 
} catch(ex) { 
result = ex.message; 
return; 
} 
adoxcatalog = null; 
} else { 
result = 'exists'; 
} 
return { 
result: result 
}; 
}, 
existsTable: function(params){ 
var connection = new ActiveXObject("ADODB.Connection"); 
var result = 'ok', exists = false; 
try{ 
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile); 
var recordset = connection.OpenSchema(20/*adSchemaTables*/); 
recordset.MoveFirst(); 
while (!recordset.EOF){ 
if (recordset("TABLE_TYPE") == "TABLE" && recordset("TABLE_NAME") == params.tablename){ 
exists = true; 
break; 
} 
recordset.MoveNext(); 
} 
recordset.Close(); 
recordset = null; 
} catch(ex){ 
result = ex.message; 
} 
return { 
"result": result, 
"exists": exists 
}; 
}, 
execute: function(params){ 
var connection = new ActiveXObject("ADODB.Connection"); 
var result = 'ok'; 
try{ 
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile); 
connection.Execute(params.sql); 
} catch(ex){ 
result = ex.message; 
} 
return { 
result: result 
}; 
}, 
query: function(params){ 
var connection = new ActiveXObject("ADODB.Connection"); 
var result = 'ok', records = []; 
try{ 
connection.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + params.accessfile); 
var recordset = new ActiveXObject("ADODB.Recordset"); 
recordset.Open(params.sql, connection); 
var fields = []; 
var enumer = new Enumerator(recordset.Fields); 
for (; !enumer.atEnd(); enumer.moveNext()){ 
fields.push(enumer.item().name); 
} 
recordset.MoveFirst(); 
while (!recordset.EOF) { 
var item = {}; 
for (var i = 0; i < fields.length; i++){ 
var fieldname = fields[i]; 
item[fieldname] = recordset(fieldname).value; 
} 
records.push(item); 
recordset.MoveNext(); 
} 
recordset.Close(); 
recordset = null; 
} catch(ex){ 
result = ex.message; 
} 
return { 
result: result, 
records: records 
}; 
} 
}; 
if (/^u/.test(typeof exports)){ // cscript 
void function(){ 
//from http://tangram.baidu.com/api.html#baidu.json 
var JSON = { 
stringify: (function () { 
/** 
* 字符串处理时需要转义的字符表 
* @private 
*/ 
var escapeMap = { 
"\b": '\\b', 
"\t": '\\t', 
"\n": '\\n', 
"\f": '\\f', 
"\r": '\\r', 
'"' : '\\"', 
"\\": '\\\\' 
}; 
/** 
* 字符串序列化 
* @private 
*/ 
function encodeString(source) { 
if (/["\\\x00-\x1f]/.test(source)) { 
source = source.replace( 
/["\\\x00-\x1f]/g, 
function (match) { 
var c = escapeMap[match]; 
if (c) { 
return c; 
} 
c = match.charCodeAt(); 
return "\\u00" 
+ Math.floor(c / 16).toString(16) 
+ (c % 16).toString(16); 
}); 
} 
return '"' + source + '"'; 
} 
/** 
* 数组序列化 
* @private 
*/ 
function encodeArray(source) { 
var result = ["["], 
l = source.length, 
preComma, i, item; 
for (i = 0; i < l; i++) { 
item = source[i]; 
switch (typeof item) { 
case "undefined": 
case "function": 
case "unknown": 
break; 
default: 
if(preComma) { 
result.push(','); 
} 
result.push(JSON.stringify(item)); 
preComma = 1; 
} 
} 
result.push("]"); 
return result.join(""); 
} 
/** 
* 处理日期序列化时的补零 
* @private 
*/ 
function pad(source) { 
return source < 10 ? '0' + source : source; 
} 
/** 
* 日期序列化 
* @private 
*/ 
function encodeDate(source){ 
return '"' + source.getFullYear() + "-" 
+ pad(source.getMonth() + 1) + "-" 
+ pad(source.getDate()) + "T" 
+ pad(source.getHours()) + ":" 
+ pad(source.getMinutes()) + ":" 
+ pad(source.getSeconds()) + '"'; 
} 
return function (value) { 
switch (typeof value) { 
case 'undefined': 
return 'undefined'; 
case 'number': 
return isFinite(value) ? String(value) : "null"; 
case 'string': 
return encodeString(value).replace(/[^\x00-\xff]/g, function(all) { 
return "\\u" + (0x10000 + all.charCodeAt(0)).toString(16).substring(1); 
}); 
case 'boolean': 
return String(value); 
default: 
if (value === null) { 
return 'null'; 
} 
if (value instanceof Array) { 
return encodeArray(value); 
} 
if (value instanceof Date) { 
return encodeDate(value); 
} 
var result = ['{'], 
encode = JSON.stringify, 
preComma, 
item; 
for (var key in value) { 
if (Object.prototype.hasOwnProperty.call(value, key)) { 
item = value[key]; 
switch (typeof item) { 
case 'undefined': 
case 'unknown': 
case 'function': 
break; 
default: 
if (preComma) { 
result.push(','); 
} 
preComma = 1; 
result.push(encode(key) + ':' + encode(item)); 
} 
} 
} 
result.push('}'); 
return result.join(''); 
} 
}; 
})(), 
parse: function (data) { 
return (new Function("return (" + data + ")"))(); 
} 
} 
//http://blog.csdn.net/cuixiping/article/details/409468 
function base64Decode(base64){ 
var xmldom = new ActiveXObject("MSXML2.DOMDocument"); 
var adostream = new ActiveXObject("ADODB.Stream"); 
var temp = xmldom.createElement("temp"); 
temp.dataType = "bin.base64"; 
temp.text = base64; 
adostream.Charset = "utf-8"; 
adostream.Type = 1; // 1=adTypeBinary 2=adTypeText 
adostream.Open(); 
adostream.Write(temp.nodeTypedValue); 
adostream.Position = 0; 
adostream.Type = 2; // 1=adTypeBinary 2=adTypeText 
var result = adostream.ReadText(-1); // -1=adReadAll 
adostream.Close(); 
adostream = null; 
xmldom = null; 
return result; 
} 
WScript.StdOut.Write('<json>'); 
var method = Access[WScript.Arguments(0)]; 
var result = null; 
if (method){ 
result = method(JSON.parse(base64Decode(WScript.Arguments(1)))); 
} 
WScript.StdOut.Write(JSON.stringify(result)); 
WScript.StdOut.Write('</json>'); 
}(); 
} else { // nodejs 
void function(){ 
function json4stdout(stdout){ 
if (!stdout) return; 
var result = null; 
String(stdout).replace(/<json>([\s\S]+)<\/json>/, function(){ 
result = JSON.parse(arguments[1]); 
}); 
return result; 
} 
var util = require('util'), exec = require('child_process').exec; 
for (var name in Access){ 
exports[name] = (function(funcname){ 
return function(params, callback){ 
console.log([funcname, params]); 
exec( 
util.format( 
'cscript.exe /e:jscript "%s" %s "%s"', __filename, 
funcname, 
(new Buffer(JSON.stringify(params))).toString('base64') 
), 
function (error, stdout, stderr) { 
if (error != null) { 
console.log('exec error: ' + error); 
return; 
} 
console.log('stdout: ' + stdout); 
callback && callback(json4stdout(stdout)); 
} 
); 
} 
})(name); 
} 
}(); 
}

调用代码：

var access = require('./access.js'); 
var util = require('util'); 
var accessfile = 'demo.mdb'; 
access.create({ accessfile: accessfile }, function(data){ 
console.log(data); 
}); 
access.existsTable({ accessfile: accessfile, tablename: 'demo' }, function(data){ 
if (data.result == 'ok' && !data.exists){ 
access.execute({ 
accessfile: 'demo.mdb', 
sql: "CREATE TABLE demo(id Counter Primary key, data Text(100))" 
}); 
} 
}); 
access.execute({ 
accessfile: 'demo.mdb', 
sql: util.format("INSERT INTO demo(data) VALUES('zswang 路过！%s')", +new Date) 
}, function(data){ 
console.log(data); 
}); 
access.query({ 
accessfile: 'demo.mdb', 
sql: "SELECT * FROM demo" 
}, function(data){ 
console.log(data); 
});

最新代码：http://code.google.com/p/nodejs-demo/source/browse/#svn%2Ftrunk%2Fdatabase