Initial Learnings Typescript

Typescript learnings

the in operator narrowing

• Typescript uses in operator to narrow down potential types

type Man = { eat: () => void };

function digest(man: Man) {
	if("eat" in man) {
		return man.eat();
	}
}

the is operator - Type predicate

• is operator is used as a type predicate to narrow that variable to that specific type if the original type is compatible

function isFish(pet: Fish | Bird): pet is Fish {
	return (pet as Fish).swim !== undefined;
}

Partial<Type>

• This utility will return a type that represents all subsets of a given type.

function updateTodo(todo: Todo, fieldsToUpdate: Partial<Todo>) {
	return { ...todo, ...fieldsToUpdate };
}

tsconfig.json we tell the typescript compiler which rules to enforce, which files to include

module-loading

References:

https://www.typescriptlang.org/docs/handbook/2/narrowing.html#using-type-predicates https://www.typescriptlang.org/docs/handbook/utility-types.html#partialtype