I believe the answer [here][1] is the answer to your question.

TL;DR;:

add the following to your `.eslintrc` file:

    &quot;env&quot;: {
        &quot;jest&quot;: true
    }


  [1]: https://stackoverflow.com/questions/31629389/how-to-use-eslint-with-jest

Are your test files under a the &quot;__test__&quot; folder? make sure jest is install properly and listed on your package.json and under scripts have:

    &quot;test&quot;: &quot;jest --coverage&quot;,
you can run the script with npm test

I&#39;m using Android Studio 3.0 Canary 4. I imported the recycler view library. Then it comes out the attr/colorError not found message.
This is app build.gradle:

    apply plugin: &#39;com.android.application&#39;
    
    android {
        compileSdkVersion 25
        buildToolsVersion &quot;25.0.3&quot;
        defaultConfig {
            applicationId &quot;com.robyn.myapplication&quot;
            minSdkVersion 19
            targetSdkVersion 25
            versionCode 1
            versionName &quot;1.0&quot;
            testInstrumentationRunner &quot;android.support.test.runner.AndroidJUnitRunner&quot;
        }
        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile(&#39;proguard-android.txt&#39;), &#39;proguard-rules.pro&#39;
            }
        }
    }
    
    dependencies {
        implementation fileTree(include: [&#39;*.jar&#39;], dir: &#39;libs&#39;)
        androidTestImplementation(&#39;com.android.support.test.espresso:espresso-core:2.2.2&#39;, {
            exclude group: &#39;com.android.support&#39;, module: &#39;support-annotations&#39;
        })
        testImplementation &#39;junit:junit:4.12&#39;
        implementation &#39;com.android.support:recyclerview-v7:26.0.0-beta2&#39;
        implementation &#39;com.android.support:appcompat-v7:26.0.0-beta2&#39;
    }

Whenever I add the two libraries implementation &#39;com.android.support:recyclerview-v7:26.0.0-beta2&#39; and 
    implementation &#39;com.android.support:appcompat-v7:26.0.0-beta2&#39;, it comes out this error message:
[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/78v0g.jpg

I tried clean and rebuild, the error message is still there. I checked res/values/colors, the color values are there. Why I get this color error? If I want to use recycler view, what version of library should I import?

attr/colorError not found error when using com.android.support:recyclerview-v7:26.0.0-beta2

I dont know how to make an API call to such a method:

    [HttpGet]
    [ActionName(&quot;GetSupport&quot;)]
    public HttpResponseMessage GetSupport(int projectid)

Because it is GET but still got a parameter to pass, how to do this?
Would it be something like this?


    let headers = new Headers();
          headers.append(&#39;Content-Type&#39;, &#39;application/json&#39;);
          headers.append(&#39;projectid&#39;, this.id);
    
          this.http.get(&#39;http://localhost:63203/api/CallCenter/GetSupport&#39;, { headers: headers })




Angular, Http GET with parameter?

I am new to jest and trying to figure out some basic stuff in my following code

    import * as actions from &#39;./IncrementalSearchActions&#39;;
    
    describe(&#39;Incremental Search Actions&#39;, () =&gt; {
        it(&#39;Should create an incremental search action&#39;)
    });

The questions/confusions I have around this are

 1. I get an error saying describe is not defined, how do I import the reuqired module?
 2. Is this supposed to be used with Karma/Jasmine?



Using jest in my react app, describe is not defined

I am new to jest and trying to figure out some basic stuff in my following code
<pre><code class="hljs language-javascript">import * as actions from './IncrementalSearchActions';

describe('Incremental Search Actions', () => {
 it('Should create an incremental search action')
});
</code></pre>
The questions/confusions I have around this are
<ol>
<li>I get an error saying describe is not defined, how do I import the reuqired module?</li>
<li>Is this supposed to be used with Karma/Jasmine?</li>
</ol>

I have a FlatList that is purposefully wider then the screen width.  

The list scrolls vertically to view each row and sits in a horizontal ScrollView to access off-screen items.

The ListHeaderComponent prop is basically an x-axis label I&#39;d like to behave as a &quot;frozen header&quot;; like in a spreadsheet.

How do I make the ListHeaderComponent sticky?

How do you make the ListHeaderComponent of a React Native FlatList sticky?

I am using react for my application. I have a `div` that I would like to have a background image. But I can&#39;t get it to show.

When I include it in the `src` folder as `myapp/src/bgimage.png` it works perfectly but I&#39;ve heard that I should include it in a folder named `images` at the root level so it&#39;s `myapp/images/bgimage.png`, however this does not work for me and gives me:

&gt; You attempted to import ../images/bgimage.png which falls outside of the project src/ directory.&#39; 

Can anyone tell me the proper way to include image assets in reactJS?

Do I store Image assets in public or src in reactJS?

I&#39;m trying to mock a call to a service but I&#39;m struggeling with the following message: **The module factory of `jest.mock()` is not allowed to reference any out-of-scope variables**.

I&#39;m using babel with ES6 syntax, jest and enzyme.


I have a simple component called `Vocabulary` which gets a list of `VocabularyEntry`-Objects from a `vocabularyService` and renders it. 

    import React from &#39;react&#39;;
    import vocabularyService from &#39;../services/vocabularyService&#39;;

    export default class Vocabulary extends React.Component {

    render() {
        
        let rows = vocabularyService.vocabulary.map((v, i) =&gt; &lt;tr key={i}&gt;
                &lt;td&gt;{v.src}&lt;/td&gt;
                &lt;td&gt;{v.target}&lt;/td&gt;
            &lt;/tr&gt;
        );
        // render rows
     }
     }

The `vocabularyServise` ist very simple:
     
      import {VocabularyEntry} from &#39;../model/VocabularyEntry&#39;;

      class VocabularyService {
    
      constructor() {
           this.vocabulary = [new VocabularyEntry(&quot;a&quot;, &quot;b&quot;)];
      }
    } 
    export default new VocabularyService();`


Now I want to mock the `vocabularyService` in a test:

    import {shallow} from &#39;enzyme&#39;;
    import React from &#39;react&#39;;
    import Vocabulary from &quot;../../../src/components/Vocabulary &quot;;
    import {VocabularyEntry} from &#39;../../../src/model/VocabularyEntry&#39;

    jest.mock(&#39;../../../src/services/vocabularyService&#39;, () =&gt; ({

    vocabulary: [new VocabularyEntry(&quot;a&quot;, &quot;a1&quot;)]

    }));

    describe(&quot;Vocabulary tests&quot;, () =&gt; {

    test(&quot;renders the vocabulary&quot;, () =&gt; {
        
        let $component = shallow(&lt;Vocabulary/&gt;);

        // expect something

    });
});

Running the test causes an error: Vocabulary.spec.js: babel-plugin-jest-hoist: The module factory of `jest.mock()` is not allowed to reference any out-of-scope variables.
Invalid variable access: VocabularyEntry.

As far as I unterstood, I cannot use the VocabularyEntry because it is not declares (as jest moves the mock definition to the top of the file).

Can anyone please explain how I can fix this? I saw solutions which required the references insinde the mock-call but I do not understand how I can do this with a class file.



Service mocked with Jest causes &quot;The module factory of jest.mock() is not allowed to reference any out-of-scope variables&quot; error

I am writing an integration test for for a React application, i.e. a test that tests many components together, and I want to mock any calls to external services.

The issue is that the test seems to execute before the async callback is executed causing my tests to fail.

Is there anyway around this? Can I somehow wait for call async code to finish?



Here is some bad **pseudo** code to illustrate my point.

I would like to test that when I mount Parent, its Child component render the content that came back from an external service, which i will mock.

&lt;!-- language: lang-javascript --&gt;

    class Parent extends component
    {
         render ()
         {
             &lt;div&gt;
                &lt;Child /&gt;
             &lt;/div&gt;
         }
    }
    class Child extends component
    {
         DoStuff()
         {
             aThingThatReturnsAPromise().then((result) =&gt; {
               Store.Result = result
             })
         }
    
        render()
        {
           DoStuff()
           return(&lt;div&gt;{Store.Result}&lt;/div&gt;)
    
    
        }
    }
    function aThingThatReturnsAPromise()
    {
         return new Promise(resolve =&gt;{
              eternalService.doSomething(function callback(result) {
                   resolve(result)
              }
        }
    
    }

When I do this in my test, it fails because the It gets executed before the callback gets fired.

&lt;!-- language: lang-javascript --&gt;

    jest.mock(&#39;eternalService&#39;, () =&gt; {
        return jest.fn(() =&gt; {
            return { doSomething: jest.fn((cb) =&gt; cb(&#39;fakeReturnValue&#39;);
        });
    });
    
    describe(&#39;When rendering Parent&#39;, () =&gt; {
        var parent;
    
        beforeAll(() =&gt; {
            parent = mount(&lt;Parent /&gt;)
        });
    
        it(&#39;should display Child with response of the service&#39;, () =&gt; {
            expect(parent.html()).toMatch(&#39;fakeReturnValue&#39;)
        });
    });


How do I test this? I understand angular resolves this with zonejs, is there an equivalent approach in React?


How to make Jest wait for all asynchronous code to finish execution before expecting an assertion

I use FlatList with large number of items. I get following alert from Expo XDE.


&gt; VirtualizedList: You have a large list that is slow to update - make
&gt; sure your renderItem function renders components that follow React
&gt; performance best practices like PureComponent, shouldComponentUpdate,
&gt; etc. {&quot;dt&quot;:13861,&quot;prevDt&quot;:1498372326027,&quot;contentLength&quot;:6624}

I used some optimization approaches to my FlatList for example PureComponent, but I still get this alert. Before I will describe my optimizations, could you tell me if this alert appears always even though FlatList is optimized? Or maybe it indicated actual issues with performance? I ask because performance of my FlatList is good.

VirtualizedList: You have a large list that is slow to update

It will be the best explain in on example

`expected(someNumber).toBe(1).or.toBe(-2).or.toBe(22) // expect result is 1 or -2 or 22`

This is bad syntax, but can do sth like that in jest?

Logical OR for expected results in Jest

I&#39;m trying to write a simple test for a simple React component, and I want to use Jest to confirm that a function has been called when I simulate a click with enzyme. According to the Jest docs, I should be able to use `spyOn` to do this: [spyOn](http://facebook.github.io/jest/docs/jest-object.html#jestspyonobject-methodname).

However, when I try this, I keep getting `TypeError: Cannot read property &#39;_isMockFunction&#39; of undefined` which I take to mean that my spy is undefined. My code looks like this:

    import React, { Component } from &#39;react&#39;;
    import logo from &#39;./logo.svg&#39;;
    import &#39;./App.css&#39;;
    class App extends Component {
    
      myClickFunc = () =&gt; {
          console.log(&#39;clickity clickcty&#39;)
      }
      render() {
        return (
          &lt;div className=&quot;App&quot;&gt;
            &lt;div className=&quot;App-header&quot;&gt;
              &lt;img src={logo} className=&quot;App-logo&quot; alt=&quot;logo&quot; /&gt;
              &lt;h2&gt;Welcome to React&lt;/h2&gt;
            &lt;/div&gt;
            &lt;p className=&quot;App-intro&quot; onClick={this.myClickFunc}&gt;
              To get started, edit &lt;code&gt;src/App.js&lt;/code&gt; and save to reload.
            &lt;/p&gt;
          &lt;/div&gt;
        );
      }
    }
    
    export default App;


and in my test file:

    import React from &#39;react&#39;;
    import ReactDOM from &#39;react-dom&#39;;
    import App from &#39;./App&#39;;
    import { shallow, mount, render } from &#39;enzyme&#39;

    describe(&#39;my sweet test&#39;, () =&gt; {
     it(&#39;clicks it&#39;, () =&gt; {
        const spy = jest.spyOn(App, &#39;myClickFunc&#39;)
        const app = shallow(&lt;App /&gt;)
        const p = app.find(&#39;.App-intro&#39;)
        p.simulate(&#39;click&#39;)
        expect(spy).toHaveBeenCalled()
     })
    })

Anyone have an insight into what I&#39;m doing wrong?

Jest spyOn function called

Jest is picking up an old version of a package and thus my tests fail unless I use `--no-cache`. I can even delete the package folder from folder `node_modules` and Jest is happy to run the tests (almost all are passing).

So how do I clear the Jest cache?




How can I clear the Jest cache?

I want to use Prettier and ESLint together, but I experienced some conflicts just by using them one after another. I see that there are these three packages that seem to allow them to be used in tandem:

- `prettier-eslint`
- `eslint-plugin-prettier` 
- `eslint-config-prettier`

However, I am unsure which to use as these package names all contain `eslint` and `prettier`.

Which should I use?

What&#39;s the difference between prettier-eslint, eslint-plugin-prettier and eslint-config-prettier?

What is the difference between

    return await foo()

and

    const t = await foo();
    return t

http://eslint.org/docs/rules/no-return-await

Why no-return-await vs const x = await?

I am using React and Redux to develop a webapp and when I started up my project I got this:

    Line 13:  Unexpected use of &#39;location&#39;  no-restricted-globals
    
    Search for the keywords to learn more about each error.
I search a lot about how to resolve it, but none of the answers I found helped me, so I turned to Stack overflow. 

Does anyone know how to fix this error? I appreciate all the help I can get. 

No restricted globals

ESLint is not working for me in VS Code. I have the plugin installed in VS Code, and ESLint itself as a developer dependency in my package.json, which I have installed as well.

I modified the following option in the VS Code User Settings:

    {
      &quot;eslint.options&quot;: { &quot;configFile&quot;: &quot;C:/mypath&quot; }
    }


I have use the command `eslint --init` to add the basic `.eslintrc.json` to the main directory of my package. 

Other people were able to get ESLint feedback from VS Code using the exact same package with the exact same ESLint config file. 

I have received no feedback of any kind when directly breaking multiple rules that were all included in the recommended rule set that is by default inside of the `.eslintrc.json` file.

What am I missing?

Edit: I have tested using ESLint via command line, and everything worked as expected, with the errors found where they should have, however, these same errors never showed up in VS Code. The issue seems to be on VS Code&#39;s side and not ESLint.

ESLint not working in VS Code?

I need to disable some variable checks in `ESLint`.

Currently, I am using this code, but am not getting the desired result:

```javascript
/* eslint no-unused-vars: [&quot;error&quot;, { &quot;caughtErrorsIgnorePattern&quot;: &quot;Hey&quot; }] */
export type Hey = {
  a: string,
  b: object
}
```
Two questions:

* Is there a variant which can enable `no-unused-vars` for a block of code?

Something like...
```javascript
/* eslint rule disable&quot;*/

// I want to place my block of code, here

/* eslint rule disable&quot;*/
```

* Or could I make `Hey` a global variable so that it can be ignored everywhere?



How can I use ESLint no-unused-vars for a block of code?

As the title says, would it be possible for eslint to show warnings instead of errors on ALL of the rules? I&#39;m using Standard JS, if that information is relevant. 

Thanks!

Is it possible to show warnings instead of errors on ALL of eslint rules?

I am using vscode with Prettier 1.7.2 and Eslint 1.7.0. After every newline I get:

    [eslint] Delete &#39;cr&#39; [prettier/prettier]

This is the .eslintrc.json:

```json
{
  &quot;extends&quot;: [&quot;airbnb&quot;, &quot;plugin:prettier/recommended&quot;],
  &quot;env&quot;: {
    &quot;jest&quot;: true,
    &quot;browser&quot;: true
  },
  &quot;rules&quot;: {
    &quot;import/no-extraneous-dependencies&quot;: &quot;off&quot;,
    &quot;import/prefer-default-export&quot;: &quot;off&quot;,
    &quot;no-confusing-arrow&quot;: &quot;off&quot;,
    &quot;linebreak-style&quot;: &quot;off&quot;,
    &quot;arrow-parens&quot;: [&quot;error&quot;, &quot;as-needed&quot;],
    &quot;comma-dangle&quot;: [
      &quot;error&quot;,
      {
        &quot;arrays&quot;: &quot;always-multiline&quot;,
        &quot;objects&quot;: &quot;always-multiline&quot;,
        &quot;imports&quot;: &quot;always-multiline&quot;,
        &quot;exports&quot;: &quot;always-multiline&quot;,
        &quot;functions&quot;: &quot;ignore&quot;
      }
    ],
    &quot;no-plusplus&quot;: &quot;off&quot;
  },
  &quot;parser&quot;: &quot;babel-eslint&quot;,
  &quot;plugins&quot;: [&quot;react&quot;],
  &quot;globals&quot;: {
    &quot;browser&quot;: true,
    &quot;$&quot;: true,
    &quot;before&quot;: true,
    &quot;document&quot;: true
  }
}

```

The `.prettierrc` file:

```json
{
  &quot;printWidth&quot;: 80,
  &quot;tabWidth&quot;: 2,
  &quot;semi&quot;: true,
  &quot;singleQuote&quot;: true,
  &quot;trailingComma&quot;: &quot;es5&quot;,
  &quot;bracketSpacing&quot;: true,
  &quot;jsxBracketSameLine&quot;: false,
}
```

How can I get rid of this error?

Why do I keep getting Delete &#39;cr&#39; [prettier/prettier]?

I installed `jest v24.7.1`in my project with:

    npm install jest -D

Then I start writing some test files, However I got these eslint errors:

    &#39;describe&#39; is not defined. eslint (no-undef)
    &#39;it&#39; is not defined. eslint (no-undef)
    &#39;expect&#39; is not defined. eslint (no-undef)

eslintrc.js:

    module.exports = {
  

    env: {
        browser: true,
        es6: true
      },
      extends: [&quot;airbnb&quot;, &quot;prettier&quot;, &quot;prettier/react&quot;],
      globals: {
        Atomics: &quot;readonly&quot;,
        SharedArrayBuffer: &quot;readonly&quot;
      },
      parserOptions: {
        ecmaFeatures: {
          jsx: true
        },
        ecmaVersion: 2018,
        sourceType: &quot;module&quot;
      },
      plugins: [&quot;react&quot;],
      rules: {}
    };

Should I add another rule or a plugin to fix this?




describe is not defined when installing jest

I have this code:

```javascript
const subTotal = orderInfo.details.reduce((acc, cv) =&gt; acc += Number(cv.price) * Number(cv.quantity), 0);
```

I want to disable two ESLint types of checks for this line, **no-return-assign** and **no-param-reassign**.

I tried it this way:

```javascript
/* eslint-disable-next-line no-return-assign eslint-disable-next-line no-param-reassign */
const subTotal = orderInfo.details.reduce((acc, cv) =&gt; acc += Number(cv.price) * Number(cv.quantity), 0);

```

But my editor is still showing the **eslint(no-return-assign)** lint error.



Content Type	Original Author	Original Content on Stackoverflow
Question	tmp dev	View Question on Stackoverflow
Solution 1 - Reactjs	SunshinyDoyle	View Answer on Stackoverflow
Solution 2 - Reactjs	Julito Sanchis	View Answer on Stackoverflow

Using jest in my react app, describe is not defined

Reactjs Problem Overview

Reactjs Solutions

Solution 1 - Reactjs

Solution 2 - Reactjs

Angular, Http GET with parameter?

attr/colorError not found error when using com.android.support:recyclerview-v7:26.0.0-beta2

Attributions