TS2339: Property 'includes' does not exist on type 'string'

Add es2016.array.include to compilerOptions.lib

You should add es2016 or es7 lib complierOptions in tsconfig.json. Default TypeScript doesn't support some es6 polyfill functions

{
  "compilerOptions": {
    ...
    "lib": [
       "dom",
       "es7"
    ]
  }
}

Or change build target to es2016 if you no longer want to support ES5 anymore

{
  "compilerOptions": {
    ...
    "target" "es2016"
  }
}