Why is npm start (after create-react-app) failing to run?

Question

After I create a sample react app using create-react-app, npm start fails.

I have tried this using node 11.4 and 10.4 (npm 6.4.1)

npm install create-react-app -g
create-react-app t2
cd t2
npm start

Expected

To be able to start simple react server to hit in browser at localhost:3000

Actual

Server did not start, got this in my terminal:

 $ npm start > t2@0.1.0 start /Users/samr/dev/githubs/react/t2 > react-scripts start /Users/samr/dev/githubs/react/t2/node_modules/ajv/lib/keyword.js:65 throw new Error('custom keyword definition is invalid: ' + this.errorsText(validateDefinition.errors)); ^ Error: custom keyword definition is invalid: data.errors should be boolean at Ajv.addKeyword (/Users/samr/dev/githubs/react/t2/node_modules/ajv/lib/keyword.js:65:13) at module.exports (/Users/samr/dev/githubs/react/t2/node_modules/ajv-errors/index.js:10:7) at Object.<anonymous> (/Users/samr/dev/githubs/react/t2/node_modules/schema-utils/src/validateOptions.js:22:1) at Module._compile (internal/modules/cjs/loader.js:723:30) at Object.Module._extensions..js (internal/modules/cjs/loader.js:734:10) at Module.load (internal/modules/cjs/loader.js:620:32) at tryModuleLoad (internal/modules/cjs/loader.js:560:12) at Function.Module._load (internal/modules/cjs/loader.js:552:3) at Module.require (internal/modules/cjs/loader.js:659:17) at require (internal/modules/cjs/helpers.js:22:18) npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! t2@0.1.0 start: `react-scripts start` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the t2@0.1.0 start script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above. npm ERR! A complete log of this run can be found in: npm ERR! /Users/samr/.npm/_logs/2019-02-09T23_19_40_848Z-debug.log

Answer 1

As @atsnam has said, you can find the resolution here https://github.com/webpack/webpack/issues/8768 .

If you use yarn

add below to package.json

"resolutions": {
  "ajv": "6.8.1"
}

then run yarn install

if you use npm

npm uninstall ajv
npm install ajv@6.8.1

That worked for me

Answer 2

Quick fix is mentioned here :

• GITHUB - webpack/issues/8768

Essentially go to node_modules/ajv/lib/keyword.js and comment out lines 64 and 65.

Answer 3

just add resolutions to your package.json like this:

  { 
    "dependencies": {
      ...
    }
    "resolutions": {
      "ajv": "6.8.1"
    }
  }

then run npm install . if you use yarn, yarn install

Answer 4

As per the suggestion in Github answers the below change has enabled me to work.

To fix this error, just change:
Line 14: `errors: 'full',`
to:
Line 14: `errors: true`
in file **node_modules\ajv-errors\index.js**

Answer 5

The accepted answer didn't work for me. Instead i did this:

• deleted node_modules folder.

• cd to project parent directory.

  npm install
  npm start

This worked like a charm.