Create `.env` file in the root directory where your `package.json` file resides. And add the following:

    BROWSER=none

Now run `npm start`.

Add `BROWSER=none` to your npm start script in your `package.json` file, like this:

```json
&quot;scripts&quot;: {
  &quot;start&quot;: &quot;BROWSER=none react-scripts start&quot;,
  &quot;build&quot;: &quot;react-scripts build&quot;,
  &quot;test&quot;: &quot;react-scripts test&quot;,
  &quot;eject&quot;: &quot;react-scripts eject&quot;
},
```

Check out the CRA documentation for more configuration and environment variable options:

https://create-react-app.dev/docs/advanced-configuration/


----------

**Update/Troubleshooting:** 

In case you&#39;re having a `&#39;BROWSER&#39; is not recognized as an internal or external command, operable program or batch file` error: do an npm install of `cross-env`: 

```bash
npm install --save cross-env
```

Then, add `cross-env BROWSER=none` to your `start` script

```json
&quot;start&quot;: &quot;cross-env BROWSER=none react-scripts start&quot;,
```




For **Windows** you can edit/create a script in `package.json` like this one:
```json
&quot;start&quot;: &quot;set BROWSER=none &amp;&amp; react-scripts start&quot;
```
For **Linux** based OS, just delete the &quot;set&quot; and the &quot;&amp;&amp;&quot; and it will work: 
```json
&quot;start&quot;: &quot;BROWSER=none react-scripts start&quot;
```

I suggest doing it at the command level, so you don&#39;t have to change any files that get committed.

```
BROWSER=none npm start
```

You can add an alias for this to your shell&#39;s configuration:

```
alias myapp-start=&#39;cd /path/to/myapp &amp;&amp; BROWSER=none npm start&#39;
```


![![enter image description here][1]][1]

As the image shown, BodyParser now is deprecated, how to correct the bodyParser syntax or statement to remove the line-through?


  [1]: https://i.stack.imgur.com/NKjUy.png

BodyParser is deprecated

&lt;br&gt;
I am new to reactJS and am writing code so that before the data is loaded from DB, it will show loading message, and then after it is loaded, render components with the loaded data. To do this, I am using both useState hook and useEffect hook. Here is the code:

The problem is, useEffect is triggered twice when I check with console.log. The code is thus querying the same data twice, which should be avoided.

Below is the code that I wrote:

    import React from &#39;react&#39;;
    import &#39;./App.css&#39;;
    import {useState,useEffect} from &#39;react&#39;;
    import Postspreview from &#39;../components/Postspreview&#39;

    const indexarray=[]; //The array to which the fetched data will be pushed

    function Home() {
       const [isLoading,setLoad]=useState(true);
       useEffect(()=&gt;{
	      /*
	      Query logic to query from DB and push to indexarray
	      */
              setLoad(false);  // To indicate that the loading is complete
        })
       },[]);
       if (isLoading===true){
           console.log(&quot;Loading&quot;);
           return &lt;div&gt;This is loading...&lt;/div&gt;
       }
       else {
           console.log(&quot;Loaded!&quot;); //This is actually logged twice.
           return (
              &lt;div&gt;
                 &lt;div className=&quot;posts_preview_columns&quot;&gt;
                 {indexarray.map(indexarray=&gt;
                 &lt;Postspreview
                    username={indexarray.username}
                    idThumbnail={indexarray.profile_thumbnail}
                    nickname={indexarray.nickname}
                    postThumbnail={indexarray.photolink}
                 /&gt;
                 )}
                &lt;/div&gt;
             &lt;/div&gt;  
             );
        }
    }

    export default Home;

Can someone help me out in understanding why it is called twice, and how to fix the code properly?
Thank you very much!

React Hooks: useEffect() is called twice even if an empty array is used as an argument

I&#39;ve created a React app using `create-react-app` but whenever I start the dev server (using `npm start`), it opens up my browser. I want to make it so that it doesn&#39;t open my browser whenever I start my dev server.

How can I accomplish this?

How to disable open browser in CRA?

<p>I've created a React app using <code>create-react-app</code> but whenever I start the dev server (using <code>npm start</code>), it opens up my browser. I want to make it so that it doesn't open my browser whenever I start my dev server.</p>
<p>How can I accomplish this?</p>


I&#39;m coding a ReactJS class with Typescript and Material-ui, in a .tsx file. In one of my custom components, I want to create a reference to one of the components that I use in my custom component.

    export class MyTextField extends React.Component&lt;MyProps, MyState&gt; {
      private refTextField: React.RefObject&lt;TextField&gt;;
      constructor(props: MyProps) {
        super(props);
        this.refTextField = React.createRef();
      }

      render(): JSX.Element {
        const { id, label, value: defaultValue } = this.props;
        const { value } = this.state;
        const element = (
          &lt;TextField ref={this.refTextField} id={id} label={label} defaultValue={defaultValue} value={value} /&gt;
        );

        return element;
      }
    }


During compilation, I get an error on the declaration of my reference:

&gt; &#39;TextField&#39; refers to a value, but is being used as a type here. TS2749

I tried to put &quot;typeof TextField&quot; in my declaration, but I have another message, when valuing the ref property in my render :

&gt; Type &#39;RefObject&lt;(props: TextFieldProps) =&gt; Element&gt;&#39; is not assignable
&gt; to type &#39;((instance: HTMLDivElement | null) =&gt; void) |
&gt; RefObject&lt;HTMLDivElement&gt; | null | undefined&#39;.     Type
&gt; &#39;RefObject&lt;(props: TextFieldProps) =&gt; Element&gt;&#39; is not assignable to
&gt; type &#39;RefObject&lt;HTMLDivElement&gt;&#39;.
&gt;     Type &#39;(props: TextFieldProps) =&gt; Element&#39; is missing the following properties from type &#39;HTMLDivElement&#39;: align, addEventListener,
&gt; removeEventListener, accessKey, and 238 more. TS2322

Any ideas ?
thank you so much

ReactJS and Typescript : refers to a value, but is being used as a type here (TS2749)

 Currently starting up the server on my client side, the error above is what I have been 
 getting. I am using Typescript, React, ESlint. I can&#39;t seem to go forward since this error 
 has been haunting me. The github page for Eslint hasn&#39;t been much help either. 

This error went up after I had created the useMutation component and exported it in the 
index.ts, 
 Not sure how to get rid of this error.

    Below is my package.json
```
    {
    &quot;name&quot;: &quot;tinyhouse_client&quot;,
    &quot;version&quot;: &quot;0.1.0&quot;,
    &quot;private&quot;: true,
      &quot;dependencies&quot;: {
      &quot;@testing-library/jest-dom&quot;: &quot;^4.2.4&quot;,
      &quot;@testing-library/react&quot;: &quot;^9.3.2&quot;,
      &quot;@testing-library/user-event&quot;: &quot;^7.1.2&quot;,
      &quot;@types/jest&quot;: &quot;^24.0.0&quot;,
      &quot;@types/node&quot;: &quot;^12.0.0&quot;,
      &quot;@types/react&quot;: &quot;^16.9.35&quot;,
      &quot;@types/react-dom&quot;: &quot;^16.9.0&quot;,
      &quot;@typescript-eslint/parser&quot;: &quot;^3.0.2&quot;,
      &quot;react&quot;: &quot;^16.13.1&quot;,
      &quot;react-dom&quot;: &quot;^16.13.1&quot;,
      &quot;react-scripts&quot;: &quot;3.4.1&quot;,
      &quot;typescript&quot;: &quot;~2.23.0&quot;
      },
      &quot;resolutions&quot;: {
     &quot;@typescript-eslint/eslint-plugin&quot;: &quot;^2.23.0&quot;,
     &quot;@typescript-eslint/parser&quot;: &quot;^2.23.0&quot;,
     &quot;@typescript-eslint/typescript-estree&quot;: &quot;^2.23.0&quot;
     },
     &quot;scripts&quot;: {
     &quot;start&quot;: &quot;react-scripts start&quot;,
     &quot; build&quot;: &quot;react-scripts build&quot;,
     &quot;test&quot;: &quot;react-scripts test&quot;,
     &quot;eject&quot;: &quot;react-scripts eject&quot;
     },
     &quot;eslintConfig&quot;: {
     &quot;extends&quot;: &quot;react-app&quot;
     },
     &quot;browserslist&quot;: {
     &quot;production&quot;: [
      &quot;&gt;0.2%&quot;,
      &quot;not dead&quot;,
      &quot;not op_mini all&quot;
    ],
      &quot;development&quot;: [
      &quot;last 1 chrome version&quot;,
      &quot;last 1 firefox version&quot;,
      &quot;last 1 safari version&quot;
     ]
     },
     **strong text** &quot;proxy&quot;: &quot;http://localhost:9000&quot;
      }
```

    Below is my index.ts
```
    export * from &#39;./server&#39;;
    export * from &#39;./useQuery&#39;;
    export * from &#39;./useMutation&#39;;
```
    And my useMutation.ts

```
    import { useState } from &#39;react&#39;;
    import { server } from &#39;./server&#39;;

    interface State&lt;TData&gt; {
    data: TData | null;
    loading: boolean; 
    error: boolean;
    }

    type MutationTuple&lt;TData, TVariables&gt; = [
    (variables?: TVariables | undefined) =&gt; Promise&lt;void&gt;,
    State&lt;TData&gt;
    ];

    export const useMutation = &lt;TData = any, TVariables = any&gt;(
    query: string
    ): MutationTuple&lt;TData, TVariables&gt; =&gt; { 
    const [state, setState] = useState&lt;State&lt;TData&gt;&gt;({
    data: null,
    loading: false,
    error: false,
    })

    const fetch = async (variables?: TVariables) =&gt; {
    try {
      setState({ data: null, loading: true, error: false });

      const { data, errors } = await server.fetch&lt;TData, TVariables&gt;({ query, variables });
      if (errors &amp;&amp; errors.length) {
        throw new Error(errors[0].message);
      }

      setState({ data, loading: false, error: false });
    } catch (err) {
      setState({ data: null, loading: false, error: true });
      throw console.error(err);
    }
   }

   return [fetch, state];
};
```





Line 0: Parsing error: Cannot read property &#39;map&#39; of undefined

I am trying to present a simple user list from an API which returns this:

```
[{&quot;UserID&quot;:2,&quot;FirstName&quot;:&quot;User2&quot;},{&quot;UserID&quot;:1,&quot;FirstName&quot;:&quot;User1&quot;}]
```

I do not understand fully how to handle Axios responses with types. The TypeScript error is

&gt; Type &#39;{} | { id: number; firstName: string; }&#39; is not assignable to type &#39;IntrinsicAttributes &amp; UserListProps &amp; { children?: ReactNode; }&#39;.
&gt;
&gt; Property &#39;items&#39; is missing in type &#39;{}&#39; but required in type &#39;UserListProps&#39;.

from the `&lt;UserList /&gt;` element in the `Users.tsx` file below. Is my `User` interface wrong?

```
import React, {useEffect, useState, Fragment } from &#39;react&#39;;
import UserList from &#39;./UserList&#39;;
import axios, {AxiosResponse} from &#39;axios&#39;;

interface User {
    id: number;
    firstName: string;
}

const Users: React.FC = (props) =&gt; {
    const [users, setUserList] = useState&lt;User&gt;();

    useEffect(() =&gt; {
        // Use [] as second argument in useEffect for not rendering each time
        axios.get(&#39;http://localhost:8080/admin/users&#39;)
        .then((response: AxiosResponse) =&gt; {
            console.log(response.data);
            setUserList( response.data );
        });
    }, []);

    return (
        &lt;Fragment&gt;
            &lt;UserList {...users} /&gt;
        &lt;/Fragment&gt;

    );
};
export default Users;
```

Below is my `UserList.tsx`.
```
import React, {Fragment } from &#39;react&#39;;

interface UserListProps {
    items: {id: number, firstName: string}[];
};

const UserList: React.FC&lt;UserListProps&gt; = (props) =&gt; {
    return (
        &lt;Fragment&gt;
            &lt;ul&gt;
            {props.items.map(user =&gt; (
                &lt;li key={user.id}&gt;
                    &lt;span&gt;{user.firstName}&lt;/span&gt;
                    {/* not call delete function, just point to it
                    // set this to null in bind() */}
                &lt;/li&gt;
            ))}
            &lt;/ul&gt;
        &lt;/Fragment&gt;
    );
};

export default UserList;
```




React and TypeScript—which types for an Axios response?

I am creating a page for user to update personal data with React-Hook-Form.
Once paged is loaded, I use `useEffect` to fetch the user&#39;s current personal data and set them into default value of the form.

I put the fetched value into `defaultValue` of `&lt;Controller /&gt;`. 
However, it is just not showing in the text box.
Here is my code:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    import React, {useState, useEffect, useCallback} from &#39;react&#39;;
    import { useForm, Controller } from &#39;react-hook-form&#39;
    import { URL } from &#39;../constants&#39;;

    const UpdateUserData = props =&gt; {
        const [userData, setUserData] = useState(null);
        const { handleSubmit, control} = useForm({mode: &#39;onBlur&#39;});

        const fetchUserData = useCallback(async account =&gt; {
            const userData = await fetch(`${URL}/user/${account}`)
                                .then(res=&gt; res.json());
            console.log(userData);
            setUserData(userData);
        }, []);

        useEffect(() =&gt; {
            const account = localStorage.getItem(&#39;account&#39;);
            fetchUserData(account);
        }, [fetchUserData])

        const onSubmit = async (data) =&gt; {
            // TODO
        }

        return (
            &lt;div&gt;
                &lt;form onSubmit={handleSubmit(onSubmit)}&gt;
                    &lt;div&gt;
                        &lt;label&gt;User Name:&lt;/label&gt;
                        &lt;Controller
                            as={&lt;input type=&#39;text&#39; /&gt;}
                            control={control}
                            defaultValue={userData ? userData.name : &#39;&#39;}
                            name=&#39;name&#39;
                        /&gt;
                    &lt;/div&gt;
                    
                    &lt;div&gt;
                        &lt;label&gt;Phone:&lt;/label&gt;
                        &lt;Controller
                            as={&lt;input type=&#39;text&#39; /&gt;}
                            control={control}
                            defaultValue={userData ? userData.phone : &#39;&#39;}
                            name=&#39;phone&#39;
                        /&gt;
                    &lt;/div&gt;
                    &lt;button&gt;Submit&lt;/button&gt;
                &lt;/form&gt;
            &lt;/div&gt;
        );
    }

    export default UpdateUserData;

&lt;!-- end snippet --&gt;

The called API is working well and the value is actually set to `userData` state.

    {
      name: &quot;John&quot;,
      phone: &quot;02-98541566&quot;
      ...
    }



I also tried to `setUserData` with mock data in `useEffect()`, and it doesn&#39;t work either.
Is there any problem in my above code?  

How to change React-Hook-Form defaultValue with useEffect()?

I am getting this warning in react:

```
index.js:1 Warning: Cannot update a component (`ConnectFunction`) 
while rendering a different component (`Register`). To locate the 
bad setState() call inside `Register` 
```

I went to the locations indicated in the stack trace and removed all setstates but the warning still persists. Is it possible this could occur from redux dispatch?

my code:

register.js
```
class Register extends Component {
  render() {
    if( this.props.registerStatus === SUCCESS) { 
      // Reset register status to allow return to register page
      this.props.dispatch( resetRegisterStatus())  # THIS IS THE LINE THAT CAUSES THE ERROR ACCORDING TO THE STACK TRACE
      return &lt;Redirect push to = {HOME}/&gt;
    }
    return (
      &lt;div style = {{paddingTop: &quot;180px&quot;, background: &#39;radial-gradient(circle, rgba(106,103,103,1) 0%, rgba(36,36,36,1) 100%)&#39;, height: &quot;100vh&quot;}}&gt;
        &lt;RegistrationForm/&gt;
      &lt;/div&gt;
    );
  }
}

function mapStateToProps( state ) {
  return {
    registerStatus: state.userReducer.registerStatus
  }
}

export default connect ( mapStateToProps ) ( Register );
```

function which triggers the warning in my registerForm component called by register.js

```
handleSubmit = async () =&gt; {
    if( this.isValidForm() ) { 
      const details = {
        &quot;username&quot;: this.state.username,
        &quot;password&quot;: this.state.password,
        &quot;email&quot;: this.state.email,
        &quot;clearance&quot;: this.state.clearance
      }
      await this.props.dispatch( register(details) )
      if( this.props.registerStatus !== SUCCESS &amp;&amp; this.mounted ) {
        this.setState( {errorMsg: this.props.registerError})
        this.handleShowError()
      }
    }
    else {
      if( this.mounted ) {
        this.setState( {errorMsg: &quot;Error - registration credentials are invalid!&quot;} )
        this.handleShowError()
      }
    }
  }
```

Stacktrace:

[![Stacktrace][1]][1]


  [1]: https://i.stack.imgur.com/6kedd.png

Cannot update a component while rendering a different component warning

I&#39;m trying to figure out the difference between [NextJs][1] and [Create React App][2]. I know both are there to make our life easier while developing our Front-end Apps using [ReactJs][3].

After exploring some articles on Google, I found that the main difference is
 
&gt; NextJs provides server side rendering (SSR) while Create React App
&gt; provides client side rendering (CSR) and SSR improves performance of 
&gt; Application Loading.
&gt;

But what about other parameters from development perspective like 

**Maintainability and Scalability of the Web App developed with NextJS or CRA?**

 **Typescript and React Hooks/Redux support**? 

Or you can even Guide me if I&#39;m doing a wrong comparison?

  [1]: https://nextjs.org/
  [2]: https://create-react-app.dev/
  [3]: https://reactjs.org/
  [4]: https://medium.com/walmartlabs/the-benefits-of-server-side-rendering-over-client-side-rendering-5d07ff2cefe8#:~:text=Here%20is%20a%20very%20simple,with%20links%20to%20your%20javascript.

What is the difference between NextJs and Create React App

I am working with create-react-app + typescript + eslint application and during build have such error:
```
Line 1:8:  &#39;React&#39; was used before it was defined  @typescript-eslint/no-use-before-define
```

Code in my component starts with:
```ts
import React from &quot;react&quot;;
```

Eslint settings:
```js
module.exports = {
  parser: &quot;@typescript-eslint/parser&quot;,
  parserOptions: {
    ecmaVersion: 2020,
    sourceType: &quot;module&quot;,
    ecmaFeatures: {
      jsx: true
    }
  },
  settings: {
    react: {
      version: &quot;detect&quot;
    }
  },
  extends: [
    &quot;plugin:react/recommended&quot;,
    &quot;plugin:@typescript-eslint/recommended&quot;,
    &quot;prettier/@typescript-eslint&quot;,
    &quot;plugin:prettier/recommended&quot;
  ],
  rules: {
    &quot;@typescript-eslint/explicit-module-boundary-types&quot;: 0,
    &quot;@typescript-eslint/triple-slash-reference&quot;: 0,
    &quot;no-use-before-define&quot;: &quot;off&quot;,
    &quot;@typescript-eslint/no-use-before-define&quot;: &quot;off&quot;
  },
};
```

Some part of package.json:
```
&quot;devDependencies&quot;: {
  &quot;@typescript-eslint/eslint-plugin&quot;: &quot;^4.1.0&quot;,
  &quot;@typescript-eslint/parser&quot;: &quot;^4.1.0&quot;,
  &quot;babel-eslint&quot;: &quot;^10.1.0&quot;,
  &quot;eslint&quot;: &quot;^6.6.0&quot;,
  &quot;eslint-config-airbnb&quot;: &quot;^18.1.0&quot;,
  &quot;eslint-config-prettier&quot;: &quot;^6.11.0&quot;,
  &quot;eslint-plugin-import&quot;: &quot;^2.20.2&quot;,
  &quot;eslint-plugin-prettier&quot;: &quot;^3.1.3&quot;,
  &quot;eslint-plugin-react&quot;: &quot;^7.20.0&quot;,
  &quot;prettier&quot;: &quot;^2.0.5&quot;,
  &quot;start-server-and-test&quot;: &quot;^1.11.3&quot;
},
&quot;dependencies&quot;: {
  ...
  &quot;react-scripts&quot;: &quot;3.4.3&quot;,
  ...
}
```

**I tried:**
 - Read https://github.com/typescript-eslint/typescript-eslint/issues/2502
 - Disable @typescript-eslint/no-use-before-define and no-use-before-define in .eslintrc.js
 - Actually I tried to delete .eslintrc.js at all, but had the same error.



&#39;React&#39; was used before it was defined

I&#39;ve created a blank React project, using the command: ```npx create-react-app``` on npm v7.0.7 and Node.js v15.0.1

Installed:
- React v17.0.1,
- node-sass v5.0.0,

Then I tried to import a blank .scss file to the App component:

### File *App.js*

```
import &#39;./App.scss&#39;

function App() {
  return (
    &lt;div className=&quot;App&quot;&gt;
      App
    &lt;/div&gt;
  );
}

export default App;
```

***It throws an error:***

```
Failed to compile.

./src/App.scss (./node_modules/css-loader/dist/cjs.js??ref--5-oneOf-6-1!./node_modules/postcss-loader/src??postcss!./node_modules/resolve-url-loader??ref--5-oneOf-6-3!./node_modules/s
ass-loader/dist/cjs.js??ref--5-oneOf-6-4!./src/App.scss)
Error: Node Sass version 5.0.0 is incompatible with ^4.0.0.
```

### File *package.json*

```
{
  &quot;name&quot;: &quot;react-17-node-sass-5&quot;,
  &quot;version&quot;: &quot;0.1.0&quot;,
  &quot;private&quot;: true,
  &quot;dependencies&quot;: {
    &quot;@testing-library/jest-dom&quot;: &quot;^5.11.5&quot;,
    &quot;@testing-library/react&quot;: &quot;^11.1.0&quot;,
    &quot;@testing-library/user-event&quot;: &quot;^12.1.10&quot;,
    &quot;node-sass&quot;: &quot;^5.0.0&quot;,
    &quot;react&quot;: &quot;^17.0.1&quot;,
    &quot;react-dom&quot;: &quot;^17.0.1&quot;,
    &quot;react-scripts&quot;: &quot;4.0.0&quot;,
    &quot;web-vitals&quot;: &quot;^0.2.4&quot;
  },
 ...

  }
}
```






Error: &#39;node-sass&#39; version 5.0.0 is incompatible with ^4.0.0

I updated my project to create react app 4.0, and I&#39;m slowing moving over my files to TypeScript. I know with this new version you don&#39;t have to repetitively import React from &#39;react&#39;. However, within all of my TS files where I&#39;m not importing React I receive this error `&#39;React&#39; refers to a UMD global, but the current file is a module. Consider adding an import instead.ts(2686)`. I know I can fix it by importing React, but I thought this was no longer needed. Also, could someone explain the meaning of this error?

My basic TSX file
```
const Users = () =&gt; {
	return &lt;&gt;Teachers aka Users&lt;/&gt;;
};

export default Users;

&#39;React&#39; refers to a UMD global, but the current file is a module

I tried installing `create-react-app` using `npm i create-react-app`, `npx create-react-app new-app` and `npm init react-app new-app`, but I keep getting this error message:

```bash
You are running create-react-app 4.0.0, which is behind the latest release (4.0.1).
We no longer support global installation of Create React App.
```

How can I fix this?

Content Type	Original Author	Original Content on Stackoverflow
Question	GSP KS	View Question on Stackoverflow
Solution 1 - Reactjs	user9441203	View Answer on Stackoverflow
Solution 2 - Reactjs	Bassem	View Answer on Stackoverflow
Solution 3 - Reactjs	Frank Garcia	View Answer on Stackoverflow
Solution 4 - Reactjs	Benjamin Atkin	View Answer on Stackoverflow

How to disable open browser in CRA?

Reactjs Problem Overview

Reactjs Solutions

Solution 1 - Reactjs

Solution 2 - Reactjs

Solution 3 - Reactjs

Solution 4 - Reactjs

React Hooks: useEffect() is called twice even if an empty array is used as an argument

BodyParser is deprecated

Attributions