# 映射类型 (Mapped Types) (opens new window)
映射类型基于索引类型
type OnlyBoolsAndHorses = {
[key: string]: boolean | Horse;
};
const conforms: OnlyBoolsAndHorses = {
del: true,
rodney: false,
};
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映射类型是一种泛型类型，它通过使用keyof创建的并集来遍历一种类型的键来创建另一种类型的键：
type OptionsFlags<Type> = {
[Property in keyof Type]: boolean;
};
type FeatureFlags = {
darkMode: () => void;
newUserProfile: () => void;
};
type FeatureOptions = OptionsFlags<FeatureFlags>;
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# 映射修饰符
- ?
- readonly
将readonly属性去掉
// Removes 'readonly' attributes from a type's properties
type CreateMutable<Type> = {
-readonly [Property in keyof Type]: Type[Property];
};
type LockedAccount = {
readonly id: string;
readonly name: string;
};
type UnlockedAccount = CreateMutable<LockedAccount>;
// UnlockedAccount的类型
// type UnlockedAccount = {
// id: string;
// name: string;
// }
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将可选属性改为不可选
type Concrete<Type> = {
[Property in keyof Type]-?: Type[Property];
};
type MaybeUser = {
id: string;
name?: string;
age?: number;
};
type User = Concrete<MaybeUser>;
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