4 ms·

The compiler can't help you at all when reading and validating data at runtime. You mean you could use a library that helps you with checking the shapes?

• r3trohack3r 3y ago
  The compiler will tell you when you are accessing data you haven't validated yet. Using the json-types module above, you assign your incoming json object to the JsonObject type. Then you type narrow by validating the payload contains the properties you are using. So you can: const user = (await body.json()) as JsonObject; // This is properly type narrowed and will work if (typeof user.emailAddress === "string") { // do something with user.emailAddress } // The compiler will let you know you can't trust // user.name to be a string at this point. This // would have generated an exception at runtime // for a malformed payload if the compiler didn't // catch it. user.username.split(" ") // You can also do type narrowing with early returns if(typeof user.age !== number) { return new Error("user.age is expected to be a number"); } // You can now use user.age with type safety ```