How To Fix npm ERR! Missing script: “start.” – Definitive Guide

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The scripts property of your package.json file supports multiple built-in scripts with their preset life cycle events and also arbitrary scripts.

Cause of Error
This npm ERR! Missing script: “start” error is encountered, when you run the npm start or npm run start command by missing to add start property inside the script property in the package.json.

Solution
To resolve this issue, add the start property in package.json.

Let us see some of the possible reasons for this error to happen and its solution.

Include Start script in package.json (Quick Solution)

The start property runs a predefined set of commands specified inside the script property.
Your package.json should contain this start property inside the script property. If you fail to add this start property, it will throw npm ERR! missing script: “start” error.

Code

    //package.json
    {
        "name": "TechMam",
        "version": "1.0.0",
        "description": "TechMam Tutorials",
        "main": "index.js",
        "author": "sv",
        "dependencies": {
            "express": "^4.18.1"
        }
    }

    //index.js
    console.log("Welcome To TechMam Tutorials!!!");
    npm start

You could see the script property along with the start property is missed in the above package.json, and as a result, the below error is thrown,
Output

    npm ERR! missing script: start

    npm ERR! A complete log of this run can be found in:
    npm ERR!     C:\Users\HP\AppData\Roaming\npm-cache\_logs\2022-07-30T13_41_34_146Z-debug.log

You can fix this error by adding valid script and start properties in the package.json.

Code

    //package.json
    {
        "name": "TechMam",
        "version": "1.0.0",
        "description": "TechMam Tutorials",
        "main": "index.js",
        "scripts": {
            "start": "node index.js"
        },
        "author": "sv",
        "dependencies": {
            "express": "^4.18.1"
        }
    }
    npm start

Output

    Welcome To TechMam Tutorials!!!

Remove duplicate script property in package.json

In package.json, if you have defined a duplicate script property, there is a high chance for npm to throw npm ERR! Missing script: “start” on running npm start.

If you have added more than one script property in the package.json file, most IDE will show a warning for “duplicate object”.

Note: When you have duplicate script properties, npm will execute only the last script property by overriding the previous script properties. So commands configured in the last script property will only be executed.

If the last script property does not contain the start command and if you run npm start, then npm will throw npm ERR! Missing script: “start” error.

Code

    //package.json
    {
        "name": "TechMam",
        "version": "1.0.0",
        "description": "TechMam Tutorials",
        "main": "index.js",
        "scripts": {
            "start": "node index.js"
        },
        "scripts": {
            "dev": "gulp"
        },
        "author": "sv"
    }

    //index.js
    console.log("Welcome To TechMam");
    npm start

Output

    npm ERR! Missing script: "start"
    npm ERR!
    npm ERR! Did you mean one of these?
    npm ERR!     npm star # Mark your favourite packages
    npm ERR!     npm stars # View packages marked as favorites
    npm ERR!
    npm ERR! To see a list of scripts, run:
    npm ERR!   npm run

The above package.json file contains two script properties, and npm will only execute the last script property by overriding the previous script.

As the last script property does not contain the start property, npm threw npm ERR! Missing script: “start” error.

So you have to include only one script property contained with the start property and remove the duplicate script to resolve this issue.
Code

    //package.json
    {
        "name": "TechMam",
        "version": "1.0.0",
        "description": "TechMam Tutorials",
        "main": "index.js",
        "scripts": {
        "start": "node index.js",
        "dev": "gulp"
        },
        "author": "sv"
    }

    //index.js
    console.log("Welcome To TechMam!!!");
    npm start

Output

    Welcome To TechMam!!!

Include Server.js as an alternate to start the script

NPM command does not always require start script commands for beginning an application.
You can use the sever.js file as an alternative to start script commands.
Internally npm will run as node server.js when npm start is executed and by avoiding the npm ERR! Missing script: “start” error.
Code

    //package.json
    {
        "name": "TechMam",
        "version": "1.0.0",
        "description": "TechMam Tutorials",
        "main": "index.js",
        "author": "sv",
        "dependencies": {
            "express": "^4.18.1"
        }
    }

    //server.js
    console.log("Welcome To TechMam, Server.js executed!!!");
    //current package structure
    . 
    ├── node_modules/ 
    ├── server.js 
    ├── package-lock.json 
    └── package.json
    npm start

Output

    > [email protected] start
    > node server.js
    Welcome To TechMam, Server.js executed!!!

In the above code, package.json is not configured with start and scriptproperties but executing npm start did not throw npm ERR! Missing script: “start”.
As you see server.js is placed in the root directory, and npm executed node server.js.

Note:
This differs from the default node behaviour of the running file specified in the package’s main attribute when executing node.

Run file using the node command

You can directly run a specific file instead of using the start command to run a file to avoid this error npm ERR! Missing script: “start”.
Code

    //index.js
    console.log("Welcome To TechMam!!!");
    node index.js

Output

    Welcome To TechMam!!!

Initialize package.json in your project

On working with a new project, you need to initialize the project to have package.json.

    npm init -y

Output

    {
      "name": "tm",
      "version": "1.0.0",
      "description": "",
      "main": "index.js",
      "scripts": {
        "test": "echo \"Error: no test specified\" && exit 1"
      },
      "keywords": [],
      "author": "",
      "license": "ISC"
    }

You can use the above command to initialize a project by creating a package.json file.
Command parameter -y is used to setting the default values.

So now, if you run the npm start command, you will see npm ERR! Missing script: “start” error because default package.json configuration will not come with the start property.

To resolve this issue, please add a valid start property inside the script property inside package.json.

Use the latest version of the package

If you use create-react app, the error npm ERR! Missing script: “start” might be caused by an outdated version.

Follow the below commands to resolve this issue,

# use to uninstall old create-react-app version 
npm uninstall -g create-react-app

# use to clear your cache
npx clear-npx-cache

# use to create a normal React.js project
npx create-react-app my-app

# use to create TypeScript React.js project
npx create-react-app my-app --template typescript

If the above commands didn’t work, please use the use-npm flag and create the commands above.

# use for React.js project
npx [email protected] my-app --use-npm

# use for TypeScript React.js project
npx [email protected] my-app --template typescript --use-npm

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