usage of ! & ? in validation statements. | Angular Community | Page 1

pure tulip Dec 4, 2022, 4:51 PM

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*ngIf = "registerForm.controls.['email'].errors!['emailError']"

I have seen the usage of ! and ? at some places during validations in reactive forms. is it to check null or what is the purpose of those operators. Please explain if anybody has answer

remote jolt Dec 4, 2022, 5:01 PM

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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining, https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#non-null-assertion-operator-postfix-

Documentation - Everyday Types

The language primitives.

pure tulip Dec 4, 2022, 5:09 PM

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I know null assertion and ternary operator but what is the purpose of using it in this

zealous belfry Dec 4, 2022, 5:10 PM

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The optional chaining (?.) operator accesses an object's property or calls a function. If the object is undefined or null, it returns undefined instead of throwing an error.

worn kite Dec 4, 2022, 5:11 PM

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! is to bypass types that might have undefined or null value.

zealous belfry Dec 4, 2022, 5:11 PM

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TypeScript also has a special syntax for removing null and undefined from a type without doing any explicit checking. Writing ! after any expression is effectively a type assertion that the value isn’t null or undefined

pure tulip Dec 4, 2022, 5:12 PM

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Ok thanks for the info.

worn kite Dec 4, 2022, 5:13 PM

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You can google ! vs ? typescript. Google is your best teacher

remote jolt Dec 4, 2022, 5:14 PM

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You can also just read the links I posted, which have nothing to do with the ternary operator and explain what you asked for.

zealous belfry Dec 4, 2022, 5:22 PM

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I just copied and pasted the first lines from each of those links and added bolding. 🙂

#usage of ! & ? in validation statements.