Developing template engines for Express为Express开发模板引擎

Use the app.engine(ext, callback) method to create your own template engine. ext refers to the file extension, and callback is the template engine function, which accepts the following items as parameters: the location of the file, the options object, and the callback function.使用app.engine(ext, callback)方法创建自己的模板引擎。ext是指文件扩展名，callback是模板引擎函数，它接受以下项目作为参数：文件的位置、选项对象和回调函数。

The following code is an example of implementing a very simple template engine for rendering .ntl files.以下代码是实现用于呈现.ntl文件的非常简单的模板引擎的示例。

const fs = require('fs') // this engine requires the fs module此引擎需要fs模块
app.engine('ntl', (filePath, options, callback) => { // define the template engine定义模板引擎
  fs.readFile(filePath, (err, content) => {
    if (err) return callback(err)
    // this is an extremely simple template engine这是一个极其简单的模板引擎
    const rendered = content.toString()
      .replace('#title#', `<title>${options.title}</title>`)
      .replace('#message#', `<h1>${options.message}</h1>`)
    return callback(null, rendered)
  })
})
app.set('views', './views') // specify the views directory
app.set('view engine', 'ntl') // register the template engine

Your app will now be able to render .ntl files. Create a file named index.ntl in the views directory with the following content.您的应用程序现在将能够渲染.ntl文件。在views目录中创建一个名为index.ntl的文件，其中包含以下内容。

#title#
#message#

Then, create the following route in your app.然后，在您的应用程序中创建以下路线。

app.get('/', (req, res) => {
  res.render('index', { title: 'Hey', message: 'Hello there!' })
})

When you make a request to the home page, index.ntl will be rendered as HTML.当您向主页发出请求时，index.ntl将呈现为HTML。