Mocha supports any assertion library you want. You can take a look at how it deals with assertions here: http://mochajs.org/#assertions. I don&#39;t know which one you want to use. 

Considering you are using [Chai][1], which is pretty popular, here are some options:

&gt; Consider &quot;foo&quot; to be the target variable you want to test

Assert
---

    var assert = chai.assert;
    assert(foo) // will pass for any truthy value (!= null,!= undefined,!= &#39;&#39;,!= 0)
    // or
    assert(foo != null)
    // or
    assert.notEqual(foo, null);

In case you want to use `assert`, you don&#39;t even need Chai. Just use it. Node supports it natively: https://nodejs.org/api/assert.html#assert_assert

Should
---

    var should = require(&#39;chai&#39;).should();
    should.exist(foo); // will pass for not null and not undefined
    // or
    should.not.equal(foo, null);

Expect
---

    var expect = chai.expect;
    expect(foo).to.not.equal(null);
    // or
    expect(foo).to.not.be.null;

PS: Unrelated but on Jest there is a `toBeNull` function. You can do `expect(foo).not.toBeNull();` or `expect(foo).not.toBe(null);`


  [1]: http://chaijs.com/

This is what worked for me (using **[Expect][1]** library with **Mocha**):

    expect(myObject).toExist(&#39;Too bad when it does not.&#39;);


  [1]: https://github.com/mjackson/expect

In case, you&#39;re using Chai in addition to Mocha:

    assert.isNotNull(tea, &#39;great, time for tea!&#39;);



I&#39;m trying to iterate through all the keys in a hash, but no output is returned from the loop. `console.log()` outputs as expected. Any idea why the JSX isn&#39;t returned and outputted correct?

    var DynamicForm = React.createClass({
      getInitialState: function() {
        var items = {};
        items[1] = { name: &#39;&#39;, populate_at: &#39;&#39;, same_as: &#39;&#39;, 
                     autocomplete_from: &#39;&#39;, title: &#39;&#39; };
        items[2] = { name: &#39;&#39;, populate_at: &#39;&#39;, same_as: &#39;&#39;, 
                     autocomplete_from: &#39;&#39;, title: &#39;&#39; };
        return {  items  };
      },

      
      
      render: function() {
        return (
          &lt;div&gt;
          // {this.state.items.map(function(object, i){
          //  ^ This worked previously when items was an array.
            { Object.keys(this.state.items).forEach(function (key) {
              console.log(&#39;key: &#39;, key);  // Returns key: 1 and key: 2
              return (
                &lt;div&gt;
                  &lt;FieldName/&gt;
                  &lt;PopulateAtCheckboxes populate_at={data.populate_at} /&gt;
                &lt;/div&gt;
                );
            }, this)}
            &lt;button onClick={this.newFieldEntry}&gt;Create a new field&lt;/button&gt;
            &lt;button onClick={this.saveAndContinue}&gt;Save and Continue&lt;/button&gt;
          &lt;/div&gt;
        );
      }

React JSX: Iterating through a hash and returning JSX elements for each key

I would like to simulate the Excel autofit function in Python&#39;s xlsxwriter.  According to this url, it is not directly supported:
http://xlsxwriter.readthedocs.io/worksheet.html

However, it should be quite straightforward to loop through each cell on the sheet and determine the maximum size for the column and just use worksheet.set_column(row, col, width) to set the width.

The complications that is keeping me from just writing this are:

 1. That URL does not specify what the units are for the third argument to set_column.
 2. I can not find a way to measure the width of the item that I want to insert into the cell.
 3. xlsxwriter does not appear to have a method to read back a particular cell.  This means I need to keep track of each cell width as I write the cell.  It would be better if I could just loop through all the cells, that way a generic routine could be written.



Simulate autofit column in xslxwriter

 I&#39;m very new in javascript testing, I would like to know how to assert not null in **Mocha** framework. 

How to assert not null?

<p>I'm very new in javascript testing, I would like to know how to assert not null in <strong>Mocha</strong> framework.</p>


I have an HTTP API that returns JSON data both on success and on failure.

An example failure would look like this:

    ~ ◆ http get http://localhost:5000/api/isbn/2266202022 
    HTTP/1.1 400 BAD REQUEST
    Content-Length: 171
    Content-Type: application/json
    Server: TornadoServer/4.0
    
    {
        &quot;message&quot;: &quot;There was an issue with at least some of the supplied values.&quot;, 
        &quot;payload&quot;: {
            &quot;isbn&quot;: &quot;Could not find match for ISBN.&quot;
        }, 
        &quot;type&quot;: &quot;validation&quot;
    }

What I want to achieve in my JavaScript code is something like this:

    fetch(url)
      .then((resp) =&gt; {
         if (resp.status &gt;= 200 &amp;&amp; resp.status &lt; 300) {
           return resp.json();
         } else {
           // This does not work, since the Promise returned by `json()` is never fulfilled
           return Promise.reject(resp.json());
         }
       })
       .catch((error) =&gt; {
         // Do something with the error object
       }

fetch: Reject promise with JSON error object

I am trying to resize an image (smaller to fit screen) in my react native app but am unable to do it as it is too big.

Here is the code:

    &#39;use strict&#39;;
     
    var React = require(&#39;react-native&#39;);
    var {
      StyleSheet,
      Text,
      TextInput,
      View,
      TouchableHighlight,
      ActivityIndicatorIOS,
      Image,
      Component
    } = React;
    
    var styles = StyleSheet.create({
      description: {
        marginBottom: 20,
        fontSize: 18,
        textAlign: &#39;center&#39;,
        color: &#39;#656565&#39;
      },
      container: {
        padding: 30,
        marginTop: 65,
        alignItems: &#39;center&#39;
      },
      flowRight: {
        flexDirection: &#39;row&#39;,
        alignItems: &#39;center&#39;,
        alignSelf: &#39;stretch&#39;
      },
      buttonText: {
        fontSize: 18,
        color: &#39;white&#39;,
        alignSelf: &#39;center&#39;
      },
      button: {
        height: 36,
        flex: 1,
        flexDirection: &#39;row&#39;,
        backgroundColor: &#39;#48BBEC&#39;,
        borderColor: &#39;#48BBEC&#39;,
        borderWidth: 1,
        borderRadius: 8,
        marginBottom: 10,
        alignSelf: &#39;stretch&#39;,
        justifyContent: &#39;center&#39;
      },
      searchInput: {
        height: 36,
        padding: 4,
        marginRight: 5,
        flex: 4,
        fontSize: 18,
        borderWidth: 1,
        borderColor: &#39;#48BBEC&#39;,
        borderRadius: 8,
        color: &#39;#48BBEC&#39;
      },
      image: {
        width: 200,
        height: 220
      },
    });
    
    class SearchPage extends Component {
      render() {
        return (
          &lt;View style={styles.container}&gt;

            &lt;Image source={require(&#39;image!rclogo&#39;)} style={styles.image}/&gt;

            &lt;Text style={styles.description}&gt;
              Search for RCers!
            &lt;/Text&gt;

            &lt;Text style={styles.description}&gt;
              Search
            &lt;/Text&gt;

            &lt;View style={styles.flowRight}&gt;
    		  &lt;TextInput
    		    style={styles.searchInput}
    		    placeholder=&#39;Search by Batch, Name, Interest...&#39;/&gt;
    		  &lt;TouchableHighlight style={styles.button}
    		      underlayColor=&#39;#99d9f4&#39;&gt;
    		    &lt;Text style={styles.buttonText}&gt;Go&lt;/Text&gt;
    		  &lt;/TouchableHighlight&gt;
    		&lt;/View&gt;

    		&lt;TouchableHighlight style={styles.button}
    		    underlayColor=&#39;#99d9f4&#39;&gt;
    		  &lt;Text style={styles.buttonText}&gt;Location&lt;/Text&gt;
    		&lt;/TouchableHighlight&gt;

          &lt;/View&gt;
        );
      }
    } 

I tried to take it out of the container tag but cannot seem to understand why it will not render properly?

Can this be done with flexbox resizeMode? How do you do it? I can&#39;t find any docs on it...

Image resizing in React Native

Is there a method for clearing the `.then`s of a JavaScript `Promise` instance?

I&#39;ve written a JavaScript test framework on top of [QUnit](https://qunitjs.com/).  The framework runs tests synchronously by running each one in a `Promise`.  (Sorry for the length of this code block.  I commented it as best I can, so it feels less tedious.)

    /* Promise extension -- used for easily making an async step with a
           timeout without the Promise knowing anything about the function 
           it&#39;s waiting on */
    $$.extend(Promise, {
        asyncTimeout: function (timeToLive, errorMessage) {
            var error = new Error(errorMessage || &quot;Operation timed out.&quot;);
            var res, // resolve()
                rej, // reject()
                t,   // timeout instance
                rst, // reset timeout function
                p,   // the promise instance
                at;  // the returned asyncTimeout instance

            function createTimeout(reject, tempTtl) {
                return setTimeout(function () {
                    // triggers a timeout event on the asyncTimeout object so that,
                    // if we want, we can do stuff outside of a .catch() block
                    // (may not be needed?)
                    $$(at).trigger(&quot;timeout&quot;);

                    reject(error);
                }, tempTtl || timeToLive);
            }

            p = new Promise(function (resolve, reject) {
                if (timeToLive != -1) {
                    t = createTimeout(reject);

                    // reset function -- allows a one-time timeout different
                    //    from the one original specified
                    rst = function (tempTtl) {
                        clearTimeout(t);
                        t = createTimeout(reject, tempTtl);
                    }
                } else {
                    // timeToLive = -1 -- allow this promise to run indefinitely
                    // used while debugging
                    t = 0;
                    rst = function () { return; };
                }

                res = function () {
                    clearTimeout(t);
                    resolve();
                };

                rej = reject;
            });

            return at = {
                promise: p,
                resolve: res,
                reject: rej,
                reset: rst,
                timeout: t
            };
        }
    });

    /* framework module members... */

    test: function (name, fn, options) {
        var mod = this; // local reference to framework module since promises
                        // run code under the window object

        var defaultOptions = {
            // default max running time is 5 seconds
            timeout: 5000
        }

        options = $$.extend({}, defaultOptions, options);

        // remove timeout when debugging is enabled
        options.timeout = mod.debugging ? -1 : options.timeout;

        // call to QUnit.test()
        test(name, function (assert) {
            // tell QUnit this is an async test so it doesn&#39;t run other tests
            // until done() is called
            var done = assert.async();
            return new Promise(function (resolve, reject) {
                console.log(&quot;Beginning: &quot; + name);

                var at = Promise.asyncTimeout(options.timeout, &quot;Test timed out.&quot;);
                $$(at).one(&quot;timeout&quot;, function () {
                    // assert.fail() is just an extension I made that literally calls
                    // assert.ok(false, msg);
                    assert.fail(&quot;Test timed out&quot;);
                });

                // run test function
                var result = fn.call(mod, assert, at.reset);

                // if the test returns a Promise, resolve it before resolving the test promise
                if (result &amp;&amp; result.constructor === Promise) {
                    // catch unhandled errors thrown by the test so future tests will run
                    result.catch(function (error) {
                        var msg = &quot;Unhandled error occurred.&quot;
                        if (error) {
                            msg = error.message + &quot;\n&quot; + error.stack;
                        }

                        assert.fail(msg);
                    }).then(function () {
                        // resolve the timeout Promise
                        at.resolve();
                        resolve();
                    });
                } else {
                    // if test does not return a Promise, simply clear the timeout
                    // and resolve our test Promise
                    at.resolve();
                    resolve();
                }
            }).then(function () {
                // tell QUnit that the test is over so that it can clean up and start the next test
                done();
                console.log(&quot;Ending: &quot; + name);
            });
        });
    }

If a test times out, my timeout Promise will `assert.fail()` on the test so that the test is marked as failed, which is all well and good, but the test continues to run because the test Promise (`result`) is still waiting to resolve it.

I need a good way to cancel my test.  I can do it by creating a field on the framework module `this.cancelTest` or something, and checking every so often (e.g. at the beginning of each `then()` iteration) within the test whether to cancel out.  However, ideally, I could use `$$(at).on(&quot;timeout&quot;, /* something here */)` to clear the remaining `then()`s on my `result` variable, so that none of the rest of the test is run.

Does something like this exist?

### Quick Update ###
I tried using `Promise.race([result, at.promise])`.  It didn&#39;t work.

### Update 2 + confusion ###
To unblock me, I added a few lines with the `mod.cancelTest`/polling within the test idea.  (I also removed the event trigger.)

    return new Promise(function (resolve, reject) {
        console.log(&quot;Beginning: &quot; + name);

        var at = Promise.asyncTimeout(options.timeout, &quot;Test timed out.&quot;);
        at.promise.catch(function () {
            // end the test if it times out
            mod.cancelTest = true;
            assert.fail(&quot;Test timed out&quot;);
            resolve();
        });

        // ...
        
    }).then(function () {
        // tell QUnit that the test is over so that it can clean up and start the next test
        done();
        console.log(&quot;Ending: &quot; + name);
    });

I set a breakpoint in the `catch` statement, and it&#39;s being hit.  What&#39;s confusing me now is that the `then()` statement isn&#39;t being called.  Ideas?

### Update 3 ###
Figured the last thing out.  `fn.call()` was throwing an error which I didn&#39;t catch, so the test promise was rejecting before `at.promise.catch()` could resolve it.

Cancel a vanilla ECMAScript 6 Promise chain

I have an element defined as 

    this.clientRowName = element(by.id(&#39;CLIENT_NAME&#39;)); //page object file

I want to read the text in this element which is &quot;ABC&quot; but doing:
    var client = page.clientRowName.getText(); 

returns an object instead of a string. Is there any other way that I can get the text for the element


Protractor: element.getText() returns an object and not String

I was surprised that I couldn&#39;t find anything about abstract classes when reading up on ES6. (By &quot;abstract class&quot; I&#39;m talking about the Java meaning of it, in which an abstract class declares method signatures that a subclass must implement in order to be instantiable).

Does anyone know of any conventions that have taken hold to implement abstract classes in ES6? It would be nice to be able to catch an abstract class violation with static analysis.

If I were to raise an error at runtime to signal an attempt at abstract class instantiation, what would the error be? 

Does ECMAScript 6 have a convention for abstract classes?

Trying to 

    sudo npm install protractor -g

and the same notorious error/warning again (googled to no avail):

    gyp WARN EACCES user &quot;root&quot; does not have permission to access the dev dir &quot;/Users/dmitrizaitsev/.node-gyp/0.12.0&quot;

What seems to happen is that `node version 0.12.0` is downloaded and rebuilt, again and again during the same installation, despite of being the current node version on my machine:

    node -v
    v0.12.0

Questions:

- The directory &quot;/Users/dmitrizaitsev/.node-gyp/0.12.0&quot; is actually missing! Why such a misleading message?

- Why was this directory not created neither during the `node v0.12.0` nor during the previous successful rebuild with `node-gyp`?

- (Obviously) How can I prevent this from happening?

I run Mac OSX 10.8.5 if that is of any importance.

gyp WARN EACCES user &quot;root&quot; does not have permission to access the dev dir

I&#39;m just getting started with webpack and am having difficulty getting the [multiple-entry-points sample](https://github.com/webpack/webpack/tree/master/examples/multiple-entry-points) to build.  The webpack.config.js file in the example includes the line

     var CommonsChunkPlugin = require(&quot;../../lib/optimize/CommonsChunkPlugin&quot;);

which fails for me with the error

    Error: Cannot find module &#39;../../lib/optimize/CommonsChunkPlugin&#39;

Searching around, I found other examples of using the CommonsChunkPlugin with the expression

    var commonsPlugin = new webpack.optimize.CommonsChunkPlugin(&quot;common.js&quot;);

which fails with the error

    ReferenceError: webpack is not defined

Some more searching found a number of examples including

    var webpack = require(&#39;webpack&#39;);

and my build now fails with 

    Error: Cannot find module &#39;webpack&#39;

I&#39;m at a loss as to how to proceed. 



Error: Cannot find module &#39;webpack&#39;

In using webpack to build my project, I typically require modules in CommonJS from npm modules. I need moment-timezone in my project, however in building the package you must also build all the data from moment-timezone, which can be quite a lot. 

Additionally the build is failing with the following error:

    ERROR in ./~/moment-timezone/data/packed/latest.json
    Module parse failed: /site/node_modules/moment-timezone/data/packed/latest.json Line 2: Unexpected token :
    You may need an appropriate loader to handle this file type.
    | {
    | 	&quot;version&quot;: &quot;2015a&quot;,
    | 	&quot;zones&quot;: [
    | 		&quot;Africa/Abidjan|LMT GMT|g.8 0|01|-2ldXH.Q&quot;,
    @ ./~/moment-timezone/index.js 4:15-51

At this point I am not as concerned with the build failing, as I am about the size of the build if it actually succeeds. Though, obviously the failing build will need to be addressed too at some point.

I would appreciate any pointers on how to handle this, especially if any of you have encountered this same issue using webpack (or browserify too, probably).

How should I use moment-timezone with webpack?

I&#39;m a beginner in `Express.js` and I&#39;m confused by these two keywords: `res.end()` and `res.send()`.

Are they the same or different?

What is the difference between res.end() and res.send()?

I believe this question is similar to [this one][1] but the terminology is different. From the Mongoose 4 [documentation][2]:

&gt; We may also define our own custom document instance methods too.

    // define a schema
    var animalSchema = new Schema({ name: String, type: String });
    
    // assign a function to the &quot;methods&quot; object of our animalSchema
    animalSchema.methods.findSimilarTypes = function (cb) {
      return this.model(&#39;Animal&#39;).find({ type: this.type }, cb);
    }
&gt;Now all of our animal instances have a findSimilarTypes method available to it.


And then:


&gt; Adding static methods to a Model is simple as well. Continuing with our animalSchema:

    // assign a function to the &quot;statics&quot; object of our animalSchema
    animalSchema.statics.findByName = function (name, cb) {
      return this.find({ name: new RegExp(name, &#39;i&#39;) }, cb);
    }
    
    var Animal = mongoose.model(&#39;Animal&#39;, animalSchema);
    Animal.findByName(&#39;fido&#39;, function (err, animals) {
      console.log(animals);
    });

It seems with static methods each of the animal instances would have the `findByName` method available to it as well.  What are the `statics` and `methods` objects in a Schema? What is the difference and why would I use one over the other?


  [1]: https://stackoverflow.com/questions/23425303/what-is-the-difference-between-methods-and-statics-in-mongoose
  [2]: http://mongoosejs.com/docs/guide.html#methods

Mongoose &#39;static&#39; methods vs. &#39;instance&#39; methods

I have a [Mocha][1] test file that looks like this:

    var expect = require(&#39;chai&#39;).expect
    var muting = require(&#39;../muting&#39;)
    
    describe(&#39;muting&#39;, function () {
      describe(&#39;init()&#39;, function () {
        it(&#39;should inject an object into twitter&#39;, function () {
          var twitter = &#39;twitter&#39;
          muting.init(twitter)
          expect(muting.twitter).to.equal(twitter)
        })
      })
    })

When I run `mocha` from the CLI, it runs the test successfully.

When I run `standard` (the executable for [JavaScript Standard Style][2]) I get errors on Mocha&#39;s framework functions like so:

    standard: Use JavaScript Standard Style (https://github.com/feross/standard)   
    c:\..\test\index.js:5:0: &#39;describe&#39; is not defined.  
    c:\..\test\index.js:6:2: &#39;describe&#39; is not defined.  
    c:\..\test\index.js:7:4: &#39;it&#39; is not defined.

What&#39;s the cleanest way to make Standard not complain about these functions?


  [1]: http://mochajs.org/
  [2]: https://github.com/feross/standard



JavaScript Standard Style does not recognize Mocha

Is it possible to add breakpoints to Mocha tests using Visual Studio Code? 

Normally when debugging code, one needs to configure the launch.json, setting the program attribute to the Javascript file to execute. I am not sure how to do this for Mocha though.

Mocha breakpoints using Visual Studio Code

I&#39;m new to Mocha and I am trying to use it to test a simple React component. The test would pass if the react component doesn&#39;t have any CSS styling but throws a syntax error if the tag within the React component contains any className:

Testing.react.js

    import React from &#39;react&#39;;
    
    export default class Testing extends React.Component {
      render() {
        return (
          &lt;section&gt;
            &lt;form&gt;
              &lt;input type=&quot;text&quot; /&gt;
            &lt;/form&gt;
          &lt;/section&gt;
        );
      }
    }

testing.jsx

    import {
      React,
      sinon,
      assert,
      expect,
      TestUtils
    } from &#39;../../test_helper&#39;;
    
    import TestingSample from &#39;../../../app/components/Testing.react.js&#39;;
    
    describe(&#39;TestingSample component&#39;, function(){
    	before(&#39;render and locate element&#39;, function(){
    		var renderedComponent = TestUtils.renderIntoDocument(
    			&lt;TestingSample /&gt;
    		);
  
    		var inputComponent = TestUtils.findRenderedDOMComponentWithTag(
    			renderedComponent, &#39;input&#39;
    		);
    
    		this.inputElement = inputComponent.getDOMNode();
    	});
    
    	it(&#39;&lt;input&gt; should be of type &quot;text&quot;&#39;, function () {
    		assert(this.inputElement.getAttribute(&#39;type&#39;) === &#39;text&#39;);
    	});
    })
The test would pass: 

    &gt; mocha --opts ./test/javascripts/mocha.opts --compilers js:babel/register --recursive test/javascripts/**/*.jsx
    
    
      TestSample component
        ✓ &lt;input&gt; should be of type &quot;text&quot;
    
    
      1 passing (44ms)

after I added the className inside of the input tag an error shows up: 

    import React from &#39;react&#39;;
    import testingStyle from &#39;../../scss/components/landing/testing.scss&#39;;
    
    export default class Testing extends React.Component {
      render() {
        return (
          &lt;section&gt;
            &lt;form&gt;
              &lt;input type=&quot;text&quot; className=&quot;testingStyle.color&quot; placeholder=&quot;Where would you like to dine&quot; /&gt;     
            &lt;/form&gt;
          &lt;/section&gt;
        );
      }
    }
Test result:

    SyntaxError: /Users/../../../Documents/project/app/scss/components/landing/testing.scss: Unexpected token (1:0)
    &gt; 1 | .color {
        | ^
      2 | 	color: red;
      3 | }

I&#39;ve searched online but no luck so far. Am I missing something? Please help me out or point me to the right direction would be greatly appreciated. 
I&#39;m currently using:  
Node Express Server  
React  
React-router  
Webpack  
Babel  
Mocha  
Chai  
Sinon  
Sinon-Chai

Mocha testing failed due to css in webpack

I ran into a problem recently that I can&#39;t explain. I have alot of code in these tests so I&#39;m going to do my best to capture the idea here

I have tests that look like:

    describe(&#39;main page&#39;, function() {
      beforeEach(function(done){
        addUserToMongoDb(done);   // #1
      });

      afterEach(function(done) {
        removeUserFromMongoDb(done);
      });

      context(&#39;login&#39;, function() {
         it(&#39;should log the user in&#39;, function() {
           logUserIn(user_email);  // #2 - This line requires the user from the beforeEach
         });
      });

      context(&#39;preferences&#39;, function() {
        before(function(done) {    //#3
           logUserInBeforeTest(user_email);
         });

        it(&#39;should show the preferences&#39;, function() {
           doCheckPreferences(); // #4
        });
      });
    });


The problem is, the beforeEach by `#1` runs fine. I can see it happening on the DB and the tests in `#2` pass.

However, the tests in the preferences context at `#4` fail because it cant find the user to log them in at `#3`. 

It seems that the context `before` is executed before the describe `beforeEach`, which causes them to fail. If I move `logUserIn` into the `it` block it works fine.

What could cause this?

Mocha beforeEach vs before execution

I have a code where certain tests will always fail in CI environment. I would like to disable them based on an environment condition.

How to programmatically skip a test in mocha during the runtime execution?

Content Type	Original Author	Original Content on Stackoverflow
Question	Hosar	View Question on Stackoverflow
Solution 1 - Javascript	Andre Pena	View Answer on Stackoverflow
Solution 2 - Javascript	kat	View Answer on Stackoverflow
Solution 3 - Javascript	FieryCat	View Answer on Stackoverflow

How to assert not null?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Assert

Should

Expect

Solution 2 - Javascript

Solution 3 - Javascript

Simulate autofit column in xslxwriter

React JSX: Iterating through a hash and returning JSX elements for each key

Attributions