In this Hasty Treat, Scott and Wes talk about the Typescript strict flag — what it does and why you might use it.

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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

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Hasty Treat - TypeScripts Strict Explained

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