如何在函数内的async.eachSeries循环内从多个get请求返回响应

Question

I am attempting to return a new array, created by combining arrays from several get requests. The new array returns correctly within the async.eachSeries async library function, however the parent function returns undefined.

My understanding is that the return within the parent function is running synchronously with the async.eachSeries() (before it can finish), which causes the parent function to return undefined .

var array_strings = [ “someUrl”, “someUrl”, “someUrl” ]

function get_forEachUrlString(base_url, array_strings) {
    …
    var combinedArray = [];
    var mergedArray = [];
    …
    async.eachSeries(array_strings, function(item, done) {
        …
        $.get(bas_url+item, function(data) {
            …
            combinedArray.push(data)
            done(); // stopping the async looping
            mergedArray = [].concat.apply([], combinedArray); // Merging the array of combined arrays
        });
    }, function(err) {
        if (err) {
            throw err;
        }
        console.log("All requests are done");
        console.log(mergedArray); // logs correct array
        return mergedArray
    });
    console.log(mergedArray); // logs [] empty array
    return mergedArray // Hoping this would return the newly created mergedArray
}

get_forEachUrlString(“someBaseUrl”, array_strings) // Attempting to return mergedArray

// this function tries to call the mergedArray, but returns undefined
function initialRender() {
    …
    console.log(merged) // returns undefined
} 

I have been searching for a way to get the parent function get_forEachUrlString() to return the value produced by the async.eachSeries function. I believe I will need to run a callback, but after trying several different combinations I'm still stumped.

How can I get the new array I've created, mergedArray to return from the function get_forEachUrlString() ?

EDIT: I failed to mention that I am attempting to call the returned value from get_forEachUrlString() within initialRender() . See how I fixed this in my answer below.

Answer 1

After some trial and error I was able to get this working. I was attempting to place any number of callbacks, but what I really needed to do was place the initialRender() function within the get_forEachUrlString() function and pass the new mergedArray value to the initialRender() function.

So the proper setup looks like this.

function get_forEachUrlString(base_url, array_strings) {
    …
    async.eachSeries(array_strings, function(item, done) {
        …
    }, function(err) {
        …
        mergedArray = [].concat.apply([], combinedArray);
        initialRender(mergedArray);
    });
}

get_forEachUrlString(“someBaseUrl”, array_strings)

Then the initialRender() returns what it should.