Modify Create React App TypeScript

setup.js

'use strict';

const fs = require('fs');
const path = require('path');

const paths = {
  webpackDev: path.resolve(
    `./node_modules/react-scripts-ts/config/webpack.config.dev.js`
  ),
  webpackProd: path.resolve(
    `./node_modules/react-scripts-ts/config/webpack.config.prod.js`
  ),
  jestConfig: path.resolve(
    `./node_modules/react-scripts-ts/scripts/utils/createJestConfig.js`
  ),
  tsConfig: path.resolve(`./tsconfig.json`),
};

function patchFile(file, fn) {
  const config = fs.readFileSync(file, 'utf8');
  fs.writeFileSync(file, fn(config), 'utf8');
}

// Patches
function aliasCommonDir(webpackConfig) {
  if (!webpackConfig.includes('alias: {common')) {
    webpackConfig.replace(
      `alias: {`,
      `alias: {common: ${path.resolve('./src/common')},`
    );
  }
  return webpackConfig;
}

function modifyJestModulePath(jestConfig) {
  if (!jestConfig.includes(`modulePaths: ['src/'],`)) {
    jestConfig.replace(
      `moduleNameMapper: {
        '^react-native$': 'react-native-web',
      },`,
      `moduleNameMapper: {
        '^react-native$': 'react-native-web',
      },
      modulePaths: ['src/'],`
    );
  }
  if (!jestConfig.includes(`'modulePaths',`)) {
    jestConfig.replace(
      `'snapshotSerializers',`,
      `'snapshotSerializers',
       'modulePaths',`
    );
  }
  return jestConfig;
}

function modifyTsConfig(config) {
  if (!config.includes(`"baseUrl": ".",`)) {
    config.replace(
      `"noUnusedLocals": true,`,
      `"noUnusedLocals": true, 
       "baseUrl": ".",
       "paths": {
         "common/*": ["src/common/*"]   
       }`
    );
  }
  return config;
}

patchFile(paths.webpackDev, aliasCommonDir);
patchFile(paths.webpackProd, aliasCommonDir);
patchFile(paths.jestConfig, modifyJestModulePath);
patchFile(paths.tsConfig, modifyTsConfig);