node.js - 什么时候触发请求？ http.请求()

Question

一个关于node的http.request(options, callback)方法的小问题。
我从 docs 获得了以下示例代码:

var options = {
  hostname: 'www.google.com',
  port: 80,
  path: '/upload',
  method: 'POST'
};

var req = http.request(options, function(res) {
  console.log('STATUS: ' + res.statusCode);
  console.log('HEADERS: ' + JSON.stringify(res.headers));
  res.setEncoding('utf8');
  res.on('data', function (chunk) {
    console.log('BODY: ' + chunk);
  });
});

req.on('error', function(e) {
  console.log('problem with request: ' + e.message);
});

// write data to request body
req.write('data\n');
req.write('data\n');
req.end();

问题:什么时候触发实际的 HTTP 请求？

是在将请求分配给 req 变量(第 8 行)时，还是在 req.end() 时？

Answer 1

解释在示例后面的文档中:

Note that in the example req.end() was called. With http.request() one must always call req.end() to signify that you're done with the request - even if there is no data being written to the request body.

req.end() 的调用是必须的。请注意，req 是一个 http.ClientRequest。 http.ClientRequest.prototype.end 的文档给你最后的线索:

request.end([data], [encoding])
Finishes sending the request