Error: yarn start - error Command “start” not found - reactjs

Question

yarn run v1.22.4
error Command "start" not found.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
This error comes up after I type yarn start in command prompt...
The main problem is there is no 'scripts' in package.json..
can anyone help please?

Answer 1

Here's an example package.json from one of my reactjs projects.
Depending on what environment/framework you work on, you are probably looking for the scripts object as defined below.
{
"name": "bitmex-dashboard",
"version": "0.1.0",
"private": true,
"dependencies": {
"#testing-library/jest-dom": "^4.2.4",
"#testing-library/react": "^9.3.2",
"#testing-library/user-event": "^7.1.2",
"#types/jest": "^24.0.0",
"#types/node": "^12.0.0",
"#types/react": "^16.9.41",
"#types/react-dom": "^16.9.8",
"axios": "^0.19.2",
"bitmex-realtime-api": "^0.4.3",
"form-data": "^3.0.0",
"lodash": "^4.17.15",
"react": "^16.13.1",
"react-dom": "^16.13.1",
"react-redux": "^7.2.0",
"react-scripts": "3.4.1",
"react-tradingview-widget": "^1.3.2",
"redux": "^4.0.5",
"redux-logger": "^3.0.6",
"redux-saga": "^1.1.3",
"semantic-ui-react": "^0.88.2",
"typescript": "~3.7.2",
"ws": "^7.3.1"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"devDependencies": {
"#types/lodash": "^4.14.157",
"#types/react-redux": "^7.1.9",
"#types/redux-logger": "^3.0.8",
"#types/socket.io-client": "^1.4.33",
"#types/ws": "^7.2.6",
"redux-devtools-extension": "^2.13.8"
}
}
If you are using nodejs, you want something like this:
...
"scripts":{
"start": "node index.js"
....
}
Here's a brief explanation on package.json

Answer 2

If you are creating a new react project, you may want to use create-react-app as it handles all the initial configurations and installs all the required dependencies too
https://reactjs.org/docs/create-a-new-react-app.html#create-react-app

Answer 3

When you write some code in a .js file you execute the content of that file passing it are argument in your terminal || shell to node command like this
Here I presume you have a file which is named index.js
node ./index.js
So instead of having to type this command every time you can add a script property in your package.json file so it will reference that command every time you execute in your terminal npm run start || npm start or yarn start if you are using Yarn.
This will look like this
// package.json
{
"scripts": {
"start": "node ./index.js",
}
}
Generaly you specify the entry point where you application execution must start.
You can learn more about package.json file here Creating a package.json file and The package.json guide