After playing around for a while I did get a better understanding of things, also thanks to @Andy for the [blog by Addy Osmani][1].

There are different *module systems*: AMD (RequireJS), CommonJS (Node) and the new ES6 module syntax (and the old ES5 Global system of course).

However if you want to use those in your browser you still need to load and wire those modules with some *module loader library* because browsers still do not support that. For that you could use a module loader like [RequireJS][2], [Browserify][3], [SystemJS][4] or [es6-module-loader][5]. 

SystemJS is my personal favorite because it allows you to load any module system (AMD, CommonJS, ES6) and even use them interchangably in 1 app. 

Update: In the mean time [Webpack][6] has become available and should be considered as a module loader as well.


  [1]: http://addyosmani.com/writing-modular-js/
  [2]: http://requirejs.org/
  [3]: http://browserify.org/
  [4]: https://github.com/systemjs/systemjs
  [5]: https://github.com/ModuleLoader/es6-module-loader
  [6]: https://webpack.github.io/

I know that MongoDB supports the syntax `find{array.0.field:&quot;value&quot;}`, but I specifically want to do this for the last element in the array, which means I don&#39;t know the index.  Is there some kind of operator for this, or am I out of luck?

EDIT:  To clarify, I want find() to only return documents where a field in the last element of an array matches a specific value.

MongoDB - Query on the last element of an array?

When I run the following command

    python manage.py migrate

I receive this error from django so can&#39;t step forward in my practice:

    Traceback (most recent call last):
      File &quot;manage.py&quot;, line 10, in &lt;module&gt;
        execute_from_command_line(sys.argv)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 385, in execute_from_command_line
        utility.execute()
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 377, in execute
        self.fetch_command(subcommand).run_from_argv(self.argv)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py&quot;, line 288, in run_from_argv
        self.execute(*args, **options.__dict__)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py&quot;, line 338, in execute
        output = self.handle(*args, **options)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py&quot;, line 63, in handle
        executor = MigrationExecutor(connection, self.migration_progress_callback)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/db/migrations/executor.py&quot;, line 17, in __init__
        self.loader = MigrationLoader(self.connection)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/db/migrations/loader.py&quot;, line 48, in __init__
        self.build_graph()
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/db/migrations/loader.py&quot;, line 241, in build_graph
        self.graph.add_dependency(migration, key, parent)
      File &quot;/home/nikhil/testWeb-devEnv/local/lib/python2.7/site-packages/django/db/migrations/graph.py&quot;, line 42, in add_dependency
        raise KeyError(&quot;Migration %s dependencies reference nonexistent parent node %r&quot; % (migration, parent))
    KeyError: u&quot;Migration testBolt.0001_initial dependencies reference nonexistent parent node (u&#39;delivery_boy&#39;, u&#39;0004_auto_20150221_2011&#39;)&quot;

How do I solve this problem?

Django: dependencies reference nonexistent parent node

I&#39;m still new to ES6 and module loaders and I&#39;m currently looking at combining a browserify setup with ES6. I was wondering if I would still need browserify/requirejs if I&#39;m using ES6 modules. Seems like both allow you to define modules and export them? What is the difference between browserify/requirejs modules and ES6 modules?

What is the difference between browserify/requirejs modules and ES6 modules

<p>I'm still new to ES6 and module loaders and I'm currently looking at combining a browserify setup with ES6. I was wondering if I would still need browserify/requirejs if I'm using ES6 modules. Seems like both allow you to define modules and export them? What is the difference between browserify/requirejs modules and ES6 modules?</p>


I have added the following before end of head

    &lt;script src=&#39;https://www.google.com/recaptcha/api.js&#39;&gt;&lt;/script&gt;

I have added this before end of form

    &lt;div class=&quot;g-recaptcha&quot; data-sitekey=&quot;== xxxxxx ==&quot;&gt;&lt;/div&gt;

I can see the recaptcha similar to https://developers.google.com/recaptcha/

HOwever, when user presses data without checking the checkbox, the data is submitted. Is there any other code I need to add to check if user has pressed the checkbox? Hopefully in js?

How to check in js that user has checked the checkbox in Google recaptcha?

In the following code:

    var p1 = new Promise(function (resolve, reject) {
        throw &#39;test1&#39;;
    });
    
    var p2 = new Promise(function (resolve, reject) {
        reject(&#39;test2&#39;);
    });
    
    p1.catch(function (err) {
        console.log(err); // test1
    });
    
    p2.catch(function (err) {
        console.log(err); // test2
    });

Is there any difference between using `reject` (in `p2`) from the `Promise` api, and throwing an error (in `p1`) using `throw`?

Its exactly the same?

If its the same, why we need a `reject` callback then?


Promise constructor with reject call vs throwing error

I&#39;ve recently run into a certain situation a couple of times, which I didn&#39;t know how to solve properly. Assume the following code:

    somethingAsync()
      .then( afterSomething )
      .then( afterSomethingElse )
      
    function afterSomething( amazingData ) {
      return processAsync( amazingData );
    }
    function afterSomethingElse( processedData ) {
    }

Now a situation might arise where I would want to have access to `amazingData` in `afterSomethingElse`.

One obvious solution would be to return an array or a hash from `afterSomething`, because, well, you can only return one value from a function. But I&#39;m wondering if there is a way to have `afterSomethingElse` accept 2 parameters and invoke it likewise, as that seems a lot easier to document and understand.

I&#39;m only wondering about this possibility since there is `Q.spread`, which does something similar to what I want.

How do you properly return multiple values from a Promise?

There is a proposal for introducing C# style `async-await`. I know Babel.js transpiles ES6 to ES5, but is there any way to make it transpile async-await to `ES5`?

Transpile Async Await proposal with Babel.js?

I&#39;m using the bluebird library and need to make a series of HTTP requests and need to some of the response data to the next HTTP request. I&#39;ve built a function that handles my requests called `callhttp()`. This takes a url and the body of a POST. 

I&#39;m calling it like this: 

    var payload = &#39;{&quot;Username&quot;: &quot;joe&quot;, &quot;Password&quot;: &quot;password&quot;}&#39;;
    var join = Promise.join;
    join(
        callhttp(&quot;172.16.28.200&quot;, payload),
        callhttp(&quot;172.16.28.200&quot;, payload),
        callhttp(&quot;172.16.28.200&quot;, payload),
        function (first, second, third) {
        console.log([first, second, third]);
    });
   
The first request gets an API key which needs to be passed to the second request and so on. How do get the response data from the first request? 

UPDATE

This is the `callhttp` function:

    var Promise = require(&quot;bluebird&quot;);
    var Request = Promise.promisify(require(&#39;request&#39;));
    
    function callhttp(host, body) {
    
        var options = {
            url: &#39;https://&#39; + host + &#39;/api/authorize&#39;,
            method: &quot;POST&quot;,
            headers: {
                &#39;content-type&#39;: &#39;application/json&#39;
            },
            body: body,
            strictSSL: false
        };
    
        return Request(options).spread(function (response) {
            if (response.statusCode == 200) {
               // console.log(body)
                console.log(response.connection.getPeerCertificate().subject.CN)
                return {
                    data: response.body
                };
            } else {
                // Just an example, 200 is not the only successful code
                throw new Error(&quot;HTTP Error: &quot; + response.statusCode );
            }
        });
    }

How to chain and share prior results with Promises

I have written a module (a file `my_mod.py` file residing in the folder `my_module`).
Currently, I am working in the file `cool_script.py` that resides in the folder `cur_proj`. I have opened the folder in PyCharm using File -- open (and I assume, hence, it is a PyCharm project).

In ProjectView (CMD-7), I can see my project `cur_proj` (in red) and under &quot;External Libraries&quot; I do see `my_module`. In cool_script.py, I can write 

    from my_module import my_mod as mm
 
and PyCharm even makes suggestion for my_mod. So far so good.

**However, when I try to run cool_script.py, PyCharm tells me 
*&quot;No module named my_module&quot;***

This seems strange to me, because

A) in the terminal (OS 10.10.2), in python, I can import the module no problem -- there is a corresponding entry in the PYTHONPATH in .bashrc

B) in PyCharm -- Settings -- Project cur_proj -- Project Interpreter -- CogWheel next to python interpreter -- more -- show paths for selected interpreter icon, the paths from PYTHONPATH do appear (as I think they should)

Hence, why do I get the error when I try to run cool_script.py?  -- **What am I missing?**

Notes:

- I am [not declaring a different / special python version](https://stackoverflow.com/questions/25150355/requests-module-works-in-console-but-not-script-all-other-modules-work-normall) at the top of cool_script.py
- I made sure that [the path to `my_module` is correct](https://stackoverflow.com/questions/19885821/how-do-i-import-modules-in-pycharm)
- I [put `__init__.py` files (empty files)](https://stackoverflow.com/questions/12284667/django-error-no-module-named) both in `my_module` and in `cur_proj`
- I am not using `virtualenv`


# Addendum 2015-Feb-25
When I go in PyCharm to Run -- Edit Configurations, for my current project, there are two options that are selected with a check mark: &quot;*Add content roots to PYTHONPATH*&quot; and &quot;*Add source roots to PYTHONPATH*&quot;. When I have both unchecked, I can load my module.

So it works now -- **but why**? 

Further questions emerged:

- What are &quot;content roots&quot; and what are &quot;source roots&quot;? And why does adding something to the PYTHONPATH make it somehow break?
- should I uncheck both of those options all the time (so also in the defaults, not only the project specific configurations (left panel of the Run/Debug Configurations dialog)?

PyCharm error: &#39;No Module&#39; when trying to import own module (python script)

I am getting a &#39;Module not specified&#39; error in my run config. I have no module showing in the drop down yet I can see my module no probs. The issue came about when I refactored my module name, changed the settings.gradle to new name.

Now when I go to project structure and select my module nothing shows in the screen, not even an error.

I&#39;m not 100% sure, but the icon beside my module looks like a folder with a cup and not a folder with a phone.

My exact steps -

 1. Open in Android view
 2. Refactor directory name
 3. refactor module name
 4. change settings.gradle contents: name to new name

Android Studio Run/Debug configuration error: Module not specified

I have a problem

    @import Foundation;

and I see:  
https://stackoverflow.com/questions/18947516/import-vs-import-ios-7

and I set &quot;Enable Modules&quot; to &quot;YES&quot; 

and my problem is not solved

use of @import when modules are disabled

Say I have a module (`./my-module.js`) that has an object which should be its return value:

    let values = { a: 1, b: 2, c: 3 }

    // &quot;export values&quot; results in SyntaxError: Unexpected token

So I can import them like:

    import {a} from &#39;./my-module&#39;           // a === 1
    import * as myModule from &#39;./my-module&#39; // myModule.a === 1

The only way I found is by hard coding the exports:

    export let a = values.a
    export let b = values.b
    export let c = values.c
    // or:
    export let {a, b, c} = values

Which is not dynamic.

Is it possible to export all values from an object?

ES6 export all values from object

I&#39;m using ECMAScript6 modules. What is the correct way to export/import multiple methods from a module from the options below?

Single class of static methods:

    //------ myClass.js ------

    export default class myClass {
      
      static myMethod1() {
        console.log(&#39;foo&#39;); 
      }
      
      static myMethod2(args...) {
        console.log(&#39;bar&#39;); 
      }  
      
    }

    //------ app.js ------

    import myClass from &#39;myClass&#39;;
    myClass.myMethod1();    //foo
    


Multiple exported methods:

    //------ myMethods.js ------

    export function myMethod1() {
    	console.log(&#39;foo&#39;);
    }

    export function myMethod2() {
    	console.log(&#39;bar&#39;);
    }

    //------ app.js ------
    import {myMethod1, myMethod2} from &#39;myMethods&#39;;
    myMethod1()    //foo;


    //OR
    import * as myMethods from &#39;myMethods&#39;;
    myMethods.myMethod1()    //foo;


1) Exporting:
A class of just static methods feels like a bit of a &#39;code smell&#39; but similarly exporting everything individually does feel a bit verbose. Is it simply developer preference or are there performance implications here?

2) Importing:
&#39;* as&#39; syntax is my preferred method as it allows you to use the dot notation (referencing both the module AND the method) aiding code readability. Does this have performance implications though when I may only be using 1 of the methods?

ES6 modules: Export single class of static methods OR multiple individual methods

I have been developing a site using babel-node and browserify with the babelify transform, to support ES6 syntax.

&lt;b&gt;I am just wondering, can I run this in production as&lt;/b&gt; `babel-node server` &lt;b&gt;rather than&lt;/b&gt; `node server` &lt;b&gt; What other options do I have to run ES6 in node?&lt;/b&gt;

Here are the commands I am running for build and start in development

    // npm run build
    browserify -t [babelify] client.js &gt; public/js/bundle.js&quot;,
    
    // npm start
    babel-node server.js&quot;

Here are my dev dependencies

    &quot;babel&quot;: &quot;^4.0.1&quot;,
    &quot;babelify&quot;: &quot;^5.0.3&quot;,
    &quot;browserify&quot;: &quot;^8.0.3&quot;

Is it okay to use babel-node in production

I am trying to use gulp and browserify to transform my `.jsx` files into `.js` files.

    var gulp = require(&#39;gulp&#39;);
    var browserify = require(&#39;browserify&#39;);
    var reactify = require(&#39;reactify&#39;);

    gulp.task(&#39;js&#39;, function () {
      browserify(&#39;public/javascripts/src/app.jsx&#39;)
        .transform(reactify)
        .bundle()
        .pipe(gulp.dest(&#39;public/javascripts/dist&#39;))
    });

```

The above threw `Arguments to path.resolve must be strings`. I managed to get around it by using `vinyl-source-stream`

    var source = require(&#39;vinyl-source-stream&#39;);
    ...
    .bundle()
    .source(&#39;app.js&#39;)
    ...

Why does this work? I am fairly new to nodejs and gulp. After reading the README of the project and the source code, I am still confused. Any help?

Why do I have to use vinyl-source-stream with gulp?

For example could I do:

    import React from &#39;react&#39;;
    import PanelA from &#39;./panelA.jsx&#39;;
    import PanelB from &#39;./panelB.jsx&#39;;
    
    React.render( 
      &lt;PanelA /&gt;
      &lt;PanelB /&gt;, 
      document.body  
    );

where React would render:

    body
       PanelA
       PanelB



Currently I&#39;m getting the error:

    Adjacent JSX elements must be wrapped in an enclosing tag

while transpiling with browserify and babelify

Is there a way to render multiple React components in the React.render() function?

After upgrading to version `0.14.2`, I see an error and recommendation to use [`ReactDOM.render()`][1] instead of `React.render()`, but whence do I import it?

When I don&#39;t import it and just running as it is, it shows it as `undefined`. Is it a built-in functionality or is it a 3rd party library?


  [1]: https://facebook.github.io/react/docs/top-level-api.html#reactdom

Where should ReactDOM be imported from?

I am a bit new to the task runner and bundler world and while going through things like 

&gt; Grunt, Gulp, Webpack, Browserify

, I did not feel that there is much difference between them. In other words, I feel Webpack can do everything that a task runner does. But still I got a huge examples where gulp and webpack are used together. I couldn&#39;t figure out the reason why.

Being new to this, I might be taking things in the wrong direction. It will be great if you could point out what I am missing. Any useful links are welcome.

Thanks in advance.

Task Runners (Gulp, Grunt, etc) and Bundlers (Webpack, Browserify). Why use together?

I&#39;m trying to use the new [Map][1] object from Javascript EC6, since it&#39;s already supported in the latest Firefox and Chrome versions.

But I&#39;m finding it very limited in &quot;functional&quot; programming, because it lacks classic map, filter etc. methods that would work nicely with a `[key, value]` pair. It has a forEach but that does NOT returns the callback result.

If I could transform its `map.entries()` from a MapIterator into a simple Array I could then use the standard `.map`, `.filter` with no additional hacks.

Is there a &quot;good&quot; way to transform a Javascript Iterator into an Array?
In python it&#39;s as easy as doing `list(iterator)`... but `Array(m.entries())` return an array with the Iterator as its first element!!!

**EDIT**

I forgot to specify I&#39;m looking for an answer which works wherever Map works, which means at least Chrome and Firefox (Array.from does not work in Chrome).

**PS.**

I know there&#39;s the fantastic [wu.js][2] but its dependency on traceur puts me off...


  [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
  [2]: https://fitzgen.github.io/wu.js/

Transforming a Javascript iterable into an array

How would I make an iterator out of an ES6 class in the same manner as JS1.7 `SomeClass.prototype.__iterator__ = function() {...}` syntax?

[EDIT 16:00]

The following works:

    class SomeClass {
        constructor() {
        }

        *[Symbol.iterator]() {
            yield &#39;1&#39;;
            yield &#39;2&#39;;
        }

        //*generator() {
        //}

    }

    an_instance = new SomeClass();
    for (let v of an_instance) {
        console.log(v);
    }

WebStorm flags `*[Symbol.iterator]()` with a &#39;function name expected&#39; warning directly following the asterix, but otherwise this compiles and runs fine with Traceur.  (Note WebStorm does not generate any errors for `*generator()`.)


How to make an iterator out of an ES6 class

When returning an object from an arrow function, it seems that it is necessary to use an extra set of `{}` and a `return` keyword because of an ambiguity in the grammar.

That means I can’t write `p =&gt; {foo: &quot;bar&quot;}`, but have to write `p =&gt; { return {foo: &quot;bar&quot;}; }`.

If the arrow function returns anything other than an object, the `{}` and `return` are unnecessary, e.g.: `p =&gt; &quot;foo&quot;`.

`p =&gt; {foo: &quot;bar&quot;}` returns `undefined`.

A modified `p =&gt; {&quot;foo&quot;: &quot;bar&quot;}` throws _“`SyntaxError`: unexpected token: &#39;`:`&#39;”_.

Is there something obvious I am missing?

ECMAScript 6 arrow function that returns an object

In JavaScript, `var` declarations create properties on the global object:

    var x = 15;
    console.log(window.x); // logs 15 in browser
    console.log(global.x); // logs 15 in Node.js

ES6 introduces lexical scoping with [`let`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let) declarations that have block scope.

    let x = 15;
    {
       let x = 14;
    }
    console.log(x); // logs 15;

However, do these declarations create properties on the global object?

    let x = 15;
    // what is this supposed to log in the browser according to ES6?
    console.log(window.x); // 15 in Firefox
    console.log(global.x); // undefined in Node.js with flag

Do let statements create properties on the global object?

I use the [require hook][1] of [BabelJS][2] (formerly named 6to5) to run node apps with [es6features][3]:

    // run.js
    require(&quot;babel/register&quot;);
    require(&quot;./app.js6&quot;);

I call `node run.js` to run my **app.js6**. I need to install BabelJS and provide a **run.js** for each project I&#39;d like to use es6features. I would prefer a call like `nodejs6 app.js6`. How can I achieve this system independently (Unix and Windows)?

  [1]: https://babeljs.io/docs/usage/require/
  [2]: https://babeljs.io/
  [3]: https://github.com/lukehoban/es6features#readme

Content Type	Original Author	Original Content on Stackoverflow
Question	joerideg	View Question on Stackoverflow
Solution 1 - Javascript	joerideg	View Answer on Stackoverflow

What is the difference between browserify/requirejs modules and ES6 modules

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Django: dependencies reference nonexistent parent node

MongoDB - Query on the last element of an array?

Attributions