npm install --save-dev typescript @babel/core @babel/cli @babel/plugin-proposal-class-properties @babel/preset-env @babel/preset-typescript"compilerOptions": { // Ensure that .d.ts files are created by tsc, but not .js files "declaration": true, "emitDeclarationOnly": true, // Ensure that Babel can safely transpile files in the TypeScript project "isolatedModules": true}