javascript - 循环遍历包含回调的函数

Question

我正在尝试使用 NodeJS 6.3.1 重复类似的异步函数来访问分页数据。目的是根据总行数和每页行数计算出数据的页数，然后调用 API 使用 request 包检索每页数据。

例如，如果总共 34 行，每页 10 条记录，我需要调用以下每个 URL。

www.example.com?page=1
www.example.com?page=2
www.example.com?page=3
www.example.com?page=4

鉴于每个调用都需要回调，我如何迭代它们？

Answer 1

以下是如何使用Promise.all():

// This is will be your get request function
function getRequest(url) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve(url);
    }, 2000);
  });
}

var promises = [];
var url = 'www.example.com?page=';

for (var i = 1; i < 10; i++) {
  // Creating a list of promises (get requests)
  promises.push(getRequest(url + i));
}

// After all of the promises have resolved, all of the responses will be
// concatinated into a list of responses and passed in like this:
Promise.all(promises).then(function(allResponses) {
  console.log(allResponses);
});

更新

如果您使用默认 Node 请求，getRequest() 方法将如下所示:

var request = require('request');

function getRequest(url) {
  return new Promise(function(resolve, reject) {
    request(url, function (error, response, body) {
      if (!error && response.statusCode == 200) {
        resolve(body); // or resolve(response) if that is what you are looking for
      } 
      reject(error);
    });
  });
}