package-lock-json vs package-json

package-lock.json: records the exact version of each installed package which allows you to re-install them. Future installs will be able to build an identical dependency tree.

package.json: records the minimum version you app needs. If you update the versions of a particular package, the change is not going to be reflected here.

https://stackoverflow.com/questions/45052520/do-i-need-both-package-lock-json-and-package-json 

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Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...?

class App extends React.Component {

render() {

return (

<Header />

<Content/>

);

}

}

This code throw error as follow :

./src/App.js
  Line 9:  Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?

   7 |     return (
   8 |     

>  9 |     
     |     ^
  10 |     );
  11 |   }
  12 | }

to solve that error that you need to put your component tags into elclosing tags

like this 




return (
    <div>
       <Comp1 />
       <Comp2 />
    </div>
)
or you can use the <React.Fragment>
return (
    <React.Fragment>
       <Comp1 />
       <Comp2 />
    </React.Fragment>
) 

https://reactjs.org/docs/fragments.html 

Error : verbose stack Error: ENOENT: no such file or directory, open 'Roaming\npm-cache\_npx\1768\package.json

When running npx (with any arguments, but -v is easiest to test) from the global install folder, the following error is produced.

The above error is due the white space contain in your username of PC. The command npx create-react-app doesn't work in this situation and shows error.

Solution : 

1. run npm config edit to edit your config
2. change cache path,e.g.
   from cache=D:\program file\npm-cache to cache=D:\progra~1\npm-cache