如何根据异步调用的返回值做出决策? [英] How to make decisions based on return value of async calls?

问题描述

Node.js

while(list != []) {
  apiCall.then(function(data){
    list = data;
  });

}

其中apiCall是按如下方式构造的承诺:

return new Promise(function (fulfill, reject){
        request("url", function (error, response, body){
            try {
                fulfill(body);
            } catch (error) {
                reject(error);
            }
        }, reject);
    }); 

因为api调用是异步的，所以出现了问题并且循环永远不会结束.我该如何解决这个问题?

Because the api calls are asynchronous, something goes wrong and the loop never ends. How can I fix this issue ?

推荐答案

您可以使用

You can run functions with callbacks inside the loops synchronously using SynJS. Here is a working code to illustrate:

var SynJS = require('synjs');
var request = require('request');

function myFunction1(modules) {
    var list, i=0;
    while(i<5) {
        modules.request("http://www.google.com", function (error, response, body){
            list = body;
            console.log("got it!", i, new Date());
            modules.SynJS.resume(_synjsContext); //<-- indicates that callback is finished
        });
        SynJS.wait(); //<-- wait for callback to finish
        i++;
    };
};

var modules = {
        SynJS:  SynJS,
        request:    request,
};

SynJS.run(myFunction1,null,modules,function (ret) {
    console.log('done');
});

这是结果:

got it! 0 Thu Jan 05 2017 18:17:20 GMT-0700 (Mountain Standard Time)
got it! 1 Thu Jan 05 2017 18:17:20 GMT-0700 (Mountain Standard Time)
got it! 2 Thu Jan 05 2017 18:17:21 GMT-0700 (Mountain Standard Time)
got it! 3 Thu Jan 05 2017 18:17:21 GMT-0700 (Mountain Standard Time)
got it! 4 Thu Jan 05 2017 18:17:21 GMT-0700 (Mountain Standard Time)
done

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