Record
Record<K, T>
K代表键，T代表值
type User = { firstName: string, lastName: string }
const myData:Record<string, User> = {
"123-123-123" : { firstName: "John", lastName: "Doe" },
"124-124-124" : { firstName: "Sarah", lastName: "Doe" },
"125-125-125" : { firstName: "Jane", lastName: "Smith" }
}
type User = { firstName: string, lastName: string }
type Country = "uk" | "france" | "india"
const myData:Record<Country, User> = {
"uk" : { firstName: "John", lastName: "Doe" },
"france" : { firstName: "Sarah", lastName: "Doe" },
"india" : { firstName: "Jane", lastName: "Smith" }
}
Omit
Omit<T, 联合类型> 去除，用于type类型定义去除不要的属性
type User = {
firstName: string;
lastName: string;
age: number;
lastActive: number;
}
type UserNameOnly = Omit<User, "age" | "lastActive">
type UserNameAndActive = Omit<User, "age">
const userByName:UserNameOnly = {
firstName: "John",
lastName: "Doe",
};
const userWithoutAge:UserNameAndActive = {
firstName: "John",
lastName: "Doe",
lastActive: -16302124725
}
Pick
Pick<T, 联合类型> 选取一部分需要的属性重组一个类型
type User = {
firstName: string,
lastName: string, age: number
}
type UserAge = Pick<User, "age">
let age:UserAge = { age: 1534 }
Partial <T> 全部变成可选
Required<T> 全部变成必选
keyof any 返回接口或type的联合类型
Parameters
定义函数参数组成一个元组。
const myFunction = (a: string, b: string) => { return a + b; }
type myType = Parameters<typeof myFunction>
// Equivalent to a tuple type of: // type myType = [ a: string, b: string ]
let passArray:myType = [ 'hello ', 'world' ]
myFunction(...passArray);
ReturnType
将一个函数的返回值作为type。
function sendData(a: number, b: number) {
return { a: `${a}`, b: `${b}` }
}
type Data = ReturnType<typeof sendData>
// The same as writing:
// type Data = {
// a: string,
// b: string
// }
NonNullable
从联合类型中去除null和undefined。
type myType = string | number | null | undefined
type noNulls = NonNullable<myType>
// The same as writing:
// type noNulls = string | number.
Exclude
从已有的联合类型中剔除一部分类型。
Exclude <T, U> T extends U ? never : T
Exclude < 联合类型1, 联合类型2>
联合类型1的每一个元素 extends 联合类型2 ？never : 当前元素
type myUnionType = "🍇" | "🍎" | "🫐" | "🍋"
// This works!
let lemon:myUnionType = "🍋"
// This throws an error! Type '"🍋"' is not assignable to type '"🍇" | "🍎" | "🫐"'.
let noLemonsPlease:Exclude<myUnionType, "🍋"> = "🍋"
Extract
只保留需要的联合类型。
Extract<T, U> T extends U ? T : never
Extract< 联合类型1, 联合类型2>
联合类型1的每一个元素 extends 联合类型2 ？当前元素 : never
构造一个新的联合类型
type myUnionType = "🥒" | "🥔" | "🌶" | "🌽"
let myFirstVariable:Extract<myUnionType, "🥒" | "🥔"> = "🥒"
// Type is "🥒" | "🥔"
更多知识学习见： fjolt.com/article/typ…
