tsconfig.json

{
  "compileOnSave"  : false,
  "compilerOptions": {
    "allowSyntheticDefaultImports"    : true,
    "baseUrl"                         : "./",
    "declaration"                     : true,
    "emitDecoratorMetadata"           : true,
    "esModuleInterop"                 : true,
    "experimentalDecorators"          : true,
    "forceConsistentCasingInFileNames": true,
    "importHelpers"                   : true,
    "inlineSources"                   : true,
    "lib"                             : [
      "dom",
      "es2019"
    ],
    "module"                          : "es2015",
    "moduleResolution"                : "node",
    "noImplicitAny"                   : false,
    "noUnusedLocals"                  : false,
    "outDir"                          : "./dist/commonjs",
    "sourceMap"                       : true,
    "strict"                          : true,
    "strictNullChecks"                : false,
    "target"                          : "ES2018",
    "typeRoots"                       : [
      "node_modules/@types"
    ],
    "types"                           : [
      "node"
    ]
  },
  "include"        : [
    "index.ts",
    "./src/**/*.ts"
  ],
  "exclude"        : [
    "node_modules",
    "**/*.spec.ts"
  ]
}