Check if a dependency is used in a project.

checker.js

const grep = require('shelljs').grep;
const deps = require('./package.json').dependencies;
require('shelljs').cd(`${ __dirname }/src`);

for (let dep in deps) {
  const finds = grep(dep, ['*.js', '**/*.js']);
  console.log(`${ dep }: ${ finds.length }`);
}