Nodejs Express Start Error: Error:cannot find module ' xxx ' __js

Nodejs Express Start Error: Error:cannot find module ' xxx ', this is because of missing module reference.

For example, I used ' express-session ' in my code, but I didn't add ' express-session ' dependencies to the "dependencies" item in the Package.json file.

D:\nodejs\myapp>set Debug=myapp & npm start

> myapp@0.0.0 start D:\nodejs\myapp
> Node/bin/www< c2/>module.js:340
    throw err;
    ^

error:cannot Find module ' express-session ' at
    function.module._resolvefilename (module.js:338:15)
    at Function.module._load (module.js:289:25) at
    Module.require (module.js:366:17) at
    require (module.js:385:17) At
    object.<anonymous> (d:\nodejs\myapp\app.js:6:15) at
    module._compile (module.js:435:26)
    at Object.module._extensions.. JS (module.js:442:10) at
    module.load (module.js:356:32) at
    function.module._load (module.js:313:12)
    At Module.require (module.js:366:17)

Package.json file

{
  ' name ': ' MyApp ', '
  version ': ' 0.0.0 ',
  ' private ': true,
  ' scripts ': {
    ' start ': ' Node./bin/www '
  },
  "dependencies": {"
    body-parser": "~1.15.2",
    "Cookie-parser": "~1.4.3",
    "Debug": "~2.2.0", "
    Ejs": "^2.5.5", "
    Express": "~4.14.0",
    "express-session": "^1.14.2",
    "Mongoose": "^4.7.6",
    "Morgan": "~1.7.0",
    "Serve-favicon": "~2.3.0"
  }
}

If you manually add dependencies to the Package.json file, you will need to execute it in your project directory (my directory is: D:\nodejs\myapp): NPM Install

There is another way to do this: NPM Install module name--save

D:\NODEJS\MYAPP>NPM Install express-session--save
express-session@1.14.2 node_modules\express-session
├──on-headers@1.0.1
├──cookie-signature@1.0.6
├──utils-merge@1.0.0
├──cookie@0.3.1
├──parseurl@1.3.1
├──depd@1.1.0
├──crc@3.4.1
└──uid-safe@2.1.3 (base64-url@1.3.3, random-bytes@1.0.0)

Remember to replace the ' xxx ' or ' express-session ' I mentioned here with the name of the module in the error message you encountered.

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