Node.js中Express 4.0中res.render回调参数的用途是什么? [英] What is the purpose of the res.render callback argument in Express 4.0 in Node.js?

问题描述

res.render回调参数的用途是什么?

What is the purpose of the res.render callback argument?

在哪种情况下，由于已经将模板指定为第一个参数，所以要使用这样的回调参数?

In which case would one want to use such a callback argument, since a template is already assigned as the first argument?

这是文档中的代码:

// send the rendered view to the client
res.render('index');

// if a callback is specified, the rendered HTML string has to be sent explicitly
res.render('index', function(err, html) {
  res.send(html);
});

// pass a local variable to the view
res.render('user', { name: 'Tobi' }, function(err, html) {
  // ...
});

我理解前两个参数的目的，但不明白最后一个参数.

I understand the purpose of the first two arguments, but not the last.

推荐答案

通过回调，您可以在继续发送渲染模板之前对其进行拦截.在发送给客户端之前，您可能希望将其缩小或对其进行修改.

With the callback, you can intercept the rendered template before sending it on. You might want to minify it or otherwise modify it before sending to the client.

从文档中:

如果提供了该方法，则该方法会返回可能的错误和呈现的字符串，但不会执行自动响应.

If provided, the method returns both the possible error and rendered string, but does not perform an automated response.

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