In this Hasty Treat, Scott and Wes talk about the Typescript strict flag — what it does and why you might use it. Sanity - Sponsor Sanity.io is a real-time headless CMS with a fully customizable Content Studio built in React. Get a Sanity powered site up and running in minutes at sanity.io/create. Get an awesome supercharged free developer plan on sanity.io/syntax. LogRocket - Sponsor LogRocket lets you replay what users do on your site, helping you reproduce bugs and fix issues faster. It’s an exception tracker, a session re-player and a performance monitor. Get 14 days free at logrocket.com/syntax. Show Notes 02:50 - What is it? Future versions of TypeScript may introduce additional stricter checking under this flag, so upgrades of TypeScript might result in new type errors in your program. When appropriate and possible, a corresponding flag will be added to disable that behavior. 03:26 - noImplicitAny The any type in TypeScript is exactly that - it can be anything. TypeScript will try to infer the type. When it can’t it will be any. Sometimes you need any, but if that is the case, you must explicitly type it as any. If something is implicitly any - it might be a mistake, or you forgot to type it. Risky! 06:01 - noImplicitThis You must type this - it can’t be implicitly inferred. 06:47 - strictFunctionTypes If you have a type that is a function and it doesn’t 100%. 07:44 - alwaysStrict Always turns on strict mode. You can’t do things like redeclare var variables. 09:25 - strictNullChecks Makes you check that the item is actually there before accessing a value or method from it. Imagine you filter or find on an array, or query selector a DOM element. There is a possibility that nothing is there. strictNullChecks makes you check that it’s there - like an if statement. Optional chaining is super handy here. 11:18 - strictBindCallApply 12:38 - strictPropertyInitialization 13:37 - useUnknownInCatchVariables Links https://www.typescriptlang.org/tsconfig#strict Tweet us your tasty treats! Scott’s Instagram LevelUpTutorials Instagram Wes’ Instagram Wes’ Twitter Wes’ Facebook Scott’s Twitter Make sure to include @SyntaxFM in your tweets