在父http请求中完成所有子http请求后，如何返回

Question

I'm hitting an API which returns all details on kills in a game, the first endpoint returns an id to the kill event, then a second endpoint is hit to retrieve the killer and killed names.

Because of the way this API is set up I need to make a request to first get the event ID and then wait for all id's in the returned array to get a result and then process the entire kill array:

    requestify.get(url).then(function (response) {
        var events = [];
        if (response.body && response.body.length > 0) {
            data = JSON.parse(response.body);
            if (data.hasOwnProperty('events')) {
                events = data.events.map(function(event) {
                    return this.getDataForHeroKillId(event.id, function(killInfo) {
                        return { killer: killInfo.killer, killed: killInfo.killed, timestamp: event.time };
                    });
                }.bind(this));
                console.log('events is: ', events);
            }
        }
        return Promise.all(events);
    }.bind(this));

My getKillInformation function looks like this:

KillFeed.prototype.getKillInformation = function(id, cb) {
var data = null;
    requestify.get(url).then(function (response) {
        var event = {};
        if (response.body && response.body.length > 0) {
            data = JSON.parse(response.body);
            if (data.hasOwnProperty('Killer')) {
                event = { killer: data.Killer, killed: data.Killed};
            }
        }
        cb(event);
    });
};

In the second method I was hoping that I could callback the result of each child request and then once they had all been executed my new array would hold the data. But due to the event driven nature of JS I found that my code block continues to return an empty events array as this code is obviously non blocking (understandably as blocking the event queue whilst making a HTTP request is not ideal). How can I implement this?

Answer 1

One uses promises for this.

requestify.get(url).then(function (response) {
    var events = [];

    if (response.body && response.body.length > 0) {
        var data = JSON.parse(response.body);
        if (data.hasOwnProperty('events')) {
            // Trying to process the kill information here
            events = data.events.map(function(event) {
                return this.getKillInformation(event.id).then(function(killInfo) {
                    return { killer: killInfo.killer, killed: killInfo.killed, timestamp: event['time1'] };
                });
            }.bind(this));
        }
    }

    return Promise.all(events);
});

KillFeed.prototype.getKillInformation = function(id) {
    var url = 'internal_url';
    return requestify.get(url).then(function (response) {
        if (response.body && response.body.length > 0) {
            var data = JSON.parse(response.body);
            if (data.hasOwnProperty('killer')) {
                return { killer: data.Killer, killed: data.Killed };
            }
        }
    });
};

Answer 2

You could use async and its waterfall method. Async is a NodeJS module, but it can be used in browser, too.