13个Typescript实用工具：开发人员的速查表
Typescript在类型检查方面非常强大，但有时当一些类型是其他类型的子集时，你需要为它们定义类型检查，这会变得繁琐。
让我们来看一个例子，你有两个响应类型：
UserProfileResponse
interface UserProfileResponse {
id: number;
name: string;
email: string;
phone: string;
avatar: string;
}
LoginResponse
interface LoginResponse {
id: number;
name: string;
}
我们可以为UserProfileResponse定义类型，并从中选择一些属性作为LoginResponse的类型，而不是定义相同上下文的LoginResponse和UserProfileResponse类型。
让我们了解一些实用函数，这些函数可以帮助你编写更好的代码。
Uppercase
构造一个类型，其中Type的所有属性都设置为大写。
type Role = "admin" | "user" | "guest";// Bad practice 💩
type UppercaseRole = "ADMIN" | "USER" | "GUEST";// Good practice ✅
type UppercaseRole = Uppercase<Role>; // "ADMIN" | "USER" | "GUEST"
Lowercase
构造一个类型，其中Type的所有属性都设置为小写。与Uppercase相反。
type Role = "ADMIN" | "USER" | "GUEST";// Bad practice 💩
type LowercaseRole = "admin" | "user" | "guest";// Good practice ✅
type LowercaseRole = Lowercase<Role>; // "admin" | "user" | "guest"
Capitalize
构造一个类型，其中Type的所有属性都设置为首字母大写。
type Role = "admin" | "user" | "guest";// Bad practice 💩
type CapitalizeRole = "Admin" | "User" | "Guest";// Good practice ✅
type CapitalizeRole = Capitalize<Role>; // "Admin" | "User" | "Guest"
Uncapitalize
构造一个类型，其中Type的所有属性都设置为首字母小写。与Capitalize相反。
type Role = "Admin" | "User" | "Guest";// Bad practice 💩
type UncapitalizeRole = "admin" | "user" | "guest";// Good practice ✅
type UncapitalizeRole = Uncapitalize<Role>; // "admin" | "user" | "guest"
Partial
构造一个类型，其中Type的所有属性都设置为可选。
interface User {
name: string;
age: number;
password: string;
}// Bad practice 💩
interface PartialUser {
name?: string;
age?: number;
password?: string;
}// Good practice ✅
type PartialUser = Partial<User>;
Required
构造一个类型，其中Type的所有属性都设置为必填项。与Partial相反。
interface User {
name?: string;
age?: number;
password?: string;
}// Bad practice 💩
interface RequiredUser {
name: string;
age: number;
password: string;
}// Good practice ✅
type RequiredUser = Required<User>;
Readonly
构造一个类型，其中Type的所有属性都设置为只读。
interface User {
role: string;
}// Bad practice 💩
const user: User = { role: "ADMIN" };
user.role = "USER";// Good practice ✅
type ReadonlyUser = Readonly<User>;
const user: ReadonlyUser = { role: "ADMIN" };
user.role = "USER"; // Error: Cannot assign to 'role' because it is a read-only property.
Record
构造一个类型，其中K类型的一组属性为T类型。每个K属性都映射到T类型。
interface Address {
street: string;
pin: number;
}interface Addresses {
home: Address;
office: Address;
}// Alternative ✅
type AddressesRecord = Record<"home" | "office", Address>;
Pick
只选取Type中键为联合类型键的属性。
interface User {
name: string;
age: number;
password: string;
}// Bad practice 💩
interface UserPartial {
name: string;
age: number;
}// Good practice ✅
type UserPartial = Pick<User, "name" | "age">;
Omit
省略Type中键为联合类型键的属性。
interface User {
name: string;
age: number;
password: string;
}// Bad practice 💩
interface UserPartial {
name: string;
age: number;
}// Good practice ✅
type UserPartial = Omit<User, "password">;
Exclude
构造一个类型，其中Type的所有属性都排除掉键为排除类型联合的属性。
type Role = "ADMIN" | "USER" | "GUEST";// Bad practice 💩
type NonAdminRole = "USER" | "GUEST";// Good practice ✅
type NonAdmin = Exclude<Role, "ADMIN">; // "USER" | "GUEST"
Extract
构造一个类型，其中Type的所有属性都选取键为提取类型联合的属性。
type Role = "ADMIN" | "USER" | "GUEST";// Bad practice 💩
type AdminRole = "ADMIN";// Good practice ✅
type Admin = Extract<Role, "ADMIN">; // "ADMIN"
NonNullable
构造一个类型，其中Type的所有属性都设置为非空。
type Role = "ADMIN" | "USER" | null;// Bad practice 💩
type NonNullableRole = "ADMIN" | "USER";// Good practice ✅
type NonNullableRole = NonNullable<Role>; // "ADMIN" | "USER"
译自：https://devsmitra.medium.com/13-typescript-utility-a-cheat-sheet-for-developer-9dfd23cb1bbc
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