promise-array

Promise Array 1.2.4

License: MIT

✅ All 12 tests pass

Table of Contents

Overview

• Description
• Installation
• Notes
• Example
• Tests

Content

• catch
• filter
• forEach
• map
• then

Description

A small library providing asynchronous array methods for promises.

Installation

Browser

Just download the PromiseArray.min.js and include it in an HTML <script> tag

eg:

<script src="PromiseArray.min.js"></script>

Node

npm i -S promise-array

Notes

This differs from Promise.all in that it does not wait for all the promises to resolve. As each promise resolves, it executes each method on that value.

For example, you want to update a list of values and you don't want the interface to appear frozen.

Example

var statusLine = document.querySelector('#status-line');
 
PromiseArray(listOfPromises)
  .map(a => a * 2)
  .filter(a => a < 100)
  .forEach(
    function (value) {
      var el = document.createElement('div');
      el.innerHtml = value;
      document.body.append(el);
    }
  )
  .then(
    function () {
      statusLine.innerHtml = 'Complete';
    }
  )
  .catch(
    function () {
      statusLine.innerHtml = 'Incomplete, please try again.';
    }
  )

catch ... (top)

When an item in your list does not resolve, it will not trigger a catch callback. Instead, once all the items have been attempted, you will get 2 arguments passed to the then method.

The only error which will trigger the catch method is going to be if an invalid promise is passed to the constructor.

filter ... (top)

Works the same as the default .filter function, with the exception that it can also return a Promise

var myPromises = [promise1, promise2];
PromiseArray(myPromises)
  .filter(function (value, index) {
    return value > 100;
  });

PromiseArray(myPromises)
  .map(function (value) {
    return new Promise(...)
  });

forEach ... (top)

Works the same as the default .forEach function.

var myPromises = [promise1, promise2];
PromiseArray(myPromises)
  .forEach(function (value, index) {
    // My code
  });

map ... (top)

Works the same as the default .map function, with the exception that it can also return a Promise

var myPromises = [promise1, promise2];
PromiseArray(myPromises)
  .map(function (value, index) {
    return value.toLowerCase();
  });

PromiseArray(myPromises)
  .map(function (value) {
    return new Promise(...)
  });

then ... (top)

Returns two arguments:

• An array of values
• An array of error objects

Construction of the error array item:

{
  promise : [ Rejected Promise ],
  error : [ Error ],
  index : [ Item Index ]
}

---

Tests

   1. Promise.Array: map (undefined)..................................... ✅
   2. Promise.Array: map (NaN)........................................... ✅
   3. Promise.Array: forEach (should be)................................. ✅
   4. Promise.Array: forEach (not be).................................... ✅
   5. Promise.Array: filter (not be)..................................... ✅
   6. Promise.Array: filter (should be).................................. ✅
   7. Promise.Array: map & filter (should be)............................ ✅
   8. Promise.Array: map & filter (not be)............................... ✅
   9. Promise.Array: map, filter & forEach (should be)................... ✅
  10. Promise.Array: map, filter & forEach (should not be undefined)..... ✅
  11. Promise.Array: map to promise (with rejection)..................... ✅
  12. Promise.Array: Invalid list of promises............................ ✅