zulip/static/js/tsconfig.json

{
    "compilerOptions": {
        /* Typescript 3.4 added the --incremental flag but its API is not
         * currently public so ts-loader cannot use it yet.
         * Tracking issue: https://github.com/microsoft/TypeScript/issues/29978
         */
        // "incremental": true,

        /* Basic options */
        "noEmit": true,
        "target": "es5",
        "module": "es6",
        "jsx": "preserve",
        "sourceMap": true,
        "removeComments": false,

        /* Strict type-checking */
        "strict": true,
        "noImplicitAny": true,
        "strictNullChecks": false,
        "noImplicitThis": true,
        "alwaysStrict": true,

        /* Additional checks */
        "noUnusedLocals": true,
        "noUnusedParameters": true,
        "noImplicitReturns": true,
        "noFallthroughCasesInSwitch": true,
    }
}