Example promise

Check the code folder for more comments.

If you want an extra explanation about Promise just visite the about page.

The code used in this example can be found here.

How to start

Create a folder named foobar (please use a better name; any name will do) and create folders bin and src. See example below:

+ foobar
    + bin
    + src
        - Main.hx
    - build.hxml

First example

This example is the first I would check out. It's originally from: https://www.toptal.com/javascript/javascript-promises

The complete code for you to try (without installing Haxe):

Because we copy/paste the original code from the example, we need to add two imports

import js.Browser.*;   // to make sure console.log works
import js.Promise;     // and the Promise

The promise constructor takes one argument, a callback with two parameters, resolve and reject. Do something within the callback, perhaps async, then call resolve if everything worked, otherwise call reject. Like throw in plain old JavaScript, it's customary, but not required, to reject with an Error object.

var promise = new Promise(function(resolve, reject) {
    // do a thing, possibly async, then..
    if (/* everything turned out fine */) {
        resolve("Stuff worked!");
    } else {
        reject(Error("It broke"));

And this is how to use the promise

promise.then(function(result) {
    console.log(result); // "Stuff worked!"
}, function(err) {
    console.log(err); // Error: "It broke"

You can always just copy/paste the code into your favorite editor and save it in the src folder.

Second example

This example is the next version of the first example It's originally from: https://www.toptal.com/javascript/javascript-promises

This example will let you roll (a maximum off) 3 times. If you roll a 6 it will stop rolling. If not it will continue till it does. Unless you roll more then 3 times. Then it will just mention that you were not able to roll a 6.

The tossASix function creates the promise. And it will fulfill when n is a 6. Lower then a 6 will trigger a reject.

    .then(null, logAndTossAgain)   // Roll first time
    .then(null, logAndTossAgain)   // Roll second time
    .then(logSuccess, logFailure); // Roll third and last time

This is how we use the promise. The tossASix returns the promise. It's possible to chain a couple of .then. In this example, if there is no logSuccess (null), the logAndTossAgain will create a promise again. But if there is a logSuccess it will skip "then" and show that response.

You can always just copy/paste the code into your favorite editor and save it in the src folder.

Third example

This example is from: https://developers.google.com/web/fundamentals/getting-started/primers/promises And the Nasa Example

Usually you can just copy/paste pure JavaScript examples and with little to no adjustments it will work!

In this case it will not work:

get('story.json').then(function(response) {
    console.log("Success!", response);
}).catch(function(error) {
    console.log("Failed!", error);

catch is an Haxe keyword, so you can't use that. So in this case catch is replace with catchError

getDataNASA(url).then(function(response) {
    console.log("Success!", response);
}).catchError(function(error) {
    console.error("Failed!", error);

Just remember that .catchError (or the original .catch) syntactic sugar is for .then(null, function(error) {}) ... but more readable.

get('story.json').then(function(response) {
    console.log("Success!", response);
}).then(null, function(error) {
    console.log("Failed!", error);

Works the same.

The original example works a little bit different because it loads a local file, you can find that example here.

This example can be copy/paste into your favorite editor and save it in the src folder.


the html is not that exciting, so we can keep that the same for all examples and check out the console info

    <title>Haxe JS - Promise example</title></head>

<!-- Your Haxe compiled script -->
<script type="text/javascript" src="example.js"></script>


The Haxe build file, build.hxml

There are a lot of different arguments that you are able to pass to the Haxe compiler. These arguments can also be placed into a text file of one per line with the extension hxml. This file can then be passed directly to the Haxe compiler as a build script.

# // build.hxml
-cp src
-main Main
-js bin/example.js
-dce full

Build js with Haxe

To finish and see what we have, build the file and see the result

  1. Open your terminal
  2. cd to the correct folder where you have saved the build.hxml
  3. type haxe build.hxml
  4. press enter

You could build everything directly in the terminal.

haxe -cp src -main Main -js bin/example.js -dce full

It will have the same result

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