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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