CODEWITHSUNDEEP
node.jsasynchronousconcurrency
Alex Cauthen
Alex Cauthen

Reputation: 517

Concurrently iterate over two iterables of same length

I have two iterables of the same length that I need to loop over at the same time. One iterable is a Map of custom objects, and the other is an array of objects. I need to add the contents of the array into the Map (via some helper prototype functions), preferably asynchronously and concurrently. Also, the two containers are associated to each other based on their order. So the first element in the array needs to be added to the first element in the Map.

If I was to do this synchronously it would look something like this:

var map;
var arr;
for (var i = 0; i < arr.length; i++) {
    // get our custom object, call its prototype helper function with the values
    // in the array.
    let customObj = map[i];
    customObj.setValues(arr[i])
}

Typically to loop over arrays async and concurrently I use bluebirds Promise.map. It would look something like this:

var arr
Promise.map(arr, (elem) => {
    // do whatever I need to do with that element of the array
    callAFunction(elem)
})

It would be awesome if I could do something like this:

var map;
var arr;
Promise.map(map, arr, (mapElem, arrElem) {
    let customObj = mapElem[1];
    customObj.setValue(arrElem);  
})

Does anyone know of a library or a clever way to help me accomplish this?

Thanks.

EDIT: Just want to add some clarification on the objects stored in the map. The map is keyed on a unique value, and values are associated with that unique values are what make up this object. It is defined in a similar manner to this:

module.exports = CustomObject;
function CustomObject(options) {
    // Initialize CustomObjects variables...
}

CustomObject.prototype.setValue(obj) {
    // Logic for adding values to object...
}

Upvotes: 0

Views: 347

Answers (2)

ghost23
ghost23

Reputation: 2242

if you already know, that the Map (I assume you really mean the JavaScript Map here, which is ordered) and the array have the same length, you do not need a mapping function, that takes both the array AND the map. One of both is enough, because the map function also gives you an index value:

var map;
var arr;
Promise.map(map, (mapElem, index) => {
    let customObj = mapElem[1];
    customObj.setValue(arr[index]);  
});

Upvotes: 1

Orelsanpls
Orelsanpls

Reputation: 23545

You can use the function Promise.all that execute all the given asynchronous functions.

You should know that actually node.js support fully Promises, you do not need bluebirds anymore.

Promise.all(arr.map(x => anyAsynchronousFunc(x)))
   .then((rets) => {
       // Have here all return of the asynchronous functions you did called

       // You can construct your array using the result in rets
   })
   .catch((err) => {
       // Handle the error
   });

Upvotes: 0

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