Nodejs implements com components

With the rapid development of web applications, Node.js has become one of the preferred technology frameworks for developers. In these applications, while using the front-end user interface, the back-end must also provide some services to perform some functions, such as file reading, database access, and network requests. For good developers, Node.js has become a good choice for writing custom services that are released in a modular and maintainable manner. However, during development, there are scenarios that require Node.js to interact with other programming languages. This article will discuss how to implement COM components using Node.js.

What is a COM component?

COM (Component Object Model) component is a universal binary interface using the Windows operating system, which allows different programming languages ​​to interact with other applications or objects for better integration. In Windows operating systems, applications and objects can communicate with each other through native code using COM components. Some simple examples include using Microsoft Word objects to automatically print documents and using Microsoft Excel objects to automatically add data to spreadsheets.

Implementing COM components in Node.js

While Node.js itself is a standalone free software, there are many third-party libraries available in the ecosystem that can be used to implement Windows-related tasks . COM objects in Node.js are typically instantiated using the ActiveXObject class. ActiveXObject is an object that allows automation of COM objects in JavaScript.

Install Node.js

Before you start using Node.js to implement COM components, you must first install Node.js. Go to the Node.js official website, download and follow the prompts.

Install COM object

Before you start using COM components, you must install the COM object and add it to the Windows registry. Many objects, such as ADO (ActiveX Data Objects) and CDONTS (can be used for .NET), can be downloaded and installed from Microsoft's Web site.

Let’s take Microsoft Excel as an example. You need to first go to the Microsoft official website to download and install the Excel component in Microsoft Office. Once the installation is complete, add the Excel component to the Windows registry.

Using ActiveXObject to call COM components

Using the ActiveXObject class makes it easy to call COM components from Node.js code. In JavaScript code, use the new operator to instantiate the ActiveXObject class and pass the name of the COM component that needs to be called and its version number.

The following are examples of some commonly used COM components and the applications they belong to:

'Microsoft Excel
var excel = new ActiveXObject('Excel.Application');

'Microsoft Word
var word = new ActiveXObject('Word.Application');

'Microsoft Access
var access = new ActiveXObject('Access.Application');

'Microsoft PowerPoint
var powerpoint = new ActiveXObject('PowerPoint.Application');

'Microsoft Internet Explorer 和 Windows Media Player等其他应用程序
var ie = new ActiveXObject('InternetExplorer.Application');
var wmp = new ActiveXObject('WMPlayer.OCX');

After instantiating ActiveXObject, we can use the methods and properties provided by the COM component. Here is an example of reading worksheet data from Excel:

var excel = new ActiveXObject('Excel.Application');
excel.Workbooks.Open('D:\test.xlsx');
var sheet = excel.Worksheets(1);

// 读取第一行第二列的单元格数据
var data = sheet.Cells(1, 2).Value;

console.log('读取到的数据：' + data);

excel.Quit();

Using COM components for file operations

Many COM components provide access to the file system. In Node.js, we usually use fs (file system module) to deal with files and directories. However, some operations may require the use of Windows operating system-specific methods. In this case, using COM components for file operations becomes useful.

The following are some common file operations and the COM components they use:

File properties and metadata

The COM components used to access file properties and metadata are Standard Windows Script Host (WSH) object. This COM component includes an object called FileSystemObject, which exposes a number of methods and properties for accessing file and directory properties.

Here are some examples of reading files using the WScript.Shell object (which contains methods for interacting with the system):

var wsh = new ActiveXObject('WScript.Shell');
var fso = new ActiveXObject('Scripting.FileSystemObject');

// 获取文件大小
var size = fso.GetFile('D:\test.docx').Size;

// 获取文件路径
var path = wsh.ExpandEnvironmentStrings('%USERPROFILE%') + '\Desktop';

// 获取计算机上的所有驱动器
var drives = fso.Drives;
for (var e = new Enumerator(drives); !e.atEnd(); e.moveNext()) {
    console.log(e.item().DriveLetter);
}

Accessing the database

For interacting with the database COM components are ADO and ODBC. ADO (ActiveX Data Objects) is an object model developed by Microsoft for connecting to various data sources. ODBC (Open Database Connectivity) is also an API used to connect different database systems.

Here are some examples of retrieving data from the database:

var connection = new ActiveXObject('ADODB.Connection');
connection.Open('Provider=SQLOLEDB.1;Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword;');

var recordset = new ActiveXObject('ADODB.Recordset');
recordset.Open('SELECT * FROM Customers', connection);

while (!recordset.EOF) {
    console.log('读取到的数据：' + recordset.Fields(1).Value);
    recordset.MoveNext();
}

recordset.Close();
connection.Close();

Summary

Using COM components allows us to use many languages ​​supported by the Windows environment in Node.js function, but also allows us to find new third-party libraries and components in the ecosystem. This article introduces the basics of implementing COM components in Node.js programs. I hope this helps and encourages you to try this technique and explore more possibilities!

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