重新构造做变换
数组类型的重新构造
向数组后面添加元素
type Push<Arr extends unknown[], Ele> = [...Arr, Ele];
type arr = Push<[1,2,3],4>;向数组前面添加元素
type Shift<Ele, Arr extends unknown[]> = [Ele,...Arr];
type arr = Shift<1,[2,3,4]>;合并只有两个元素的两个元组对应的元素
//合并前
type tuple1 = [1,2];
type tuple2 = ['guang', 'dong'];
//合并后
type tuple = [[1, 'guang'], [2, 'dong']];type Zip<One extends [unknown,unknown],Other extends [unknown,unknown]> =
One extends [infer OneFirst, infer OneSecond] ?
Other extends [infer OtherFirst, infer OthrtSecond] ?
[[OneFirst, OtherFirst],[OneSecond, OthrtSecond]]
: []
: []
type zip = Zip<[1,2],['guang','dong']>;合并只有任意个元素的两个元组对应的元素
type Zip<One extends unknown[],Other extends unknown[]> =
One extends [infer OneFirst, ...infer OneRest] ?
Other extends [infer OtherFirst, ...infer OthrtRest] ?
[[OneFirst, OtherFirst],...Zip<OneRest, OthrtRest>]
: []
: []
type zip = Zip<[1,2,3,4],['a','b','c','d']>;字符串的重新构造
将字符串第一个元素转换成大写
type CapitalizeStrb<Str extends string> =
Str extends `${infer First}${infer Rest}` ?
`${Uppercase<First>}${Rest}`
: Str
type str = CapitalizeStrb<'abc'>;删除字符串中的某个字串
type DropSubStr<Str extends string, SubStr extends string> =
Str extends `${infer Prefix}${SubStr}${infer Suffix}`?
DropSubStr<`${Prefix}${Suffix}`,SubStr>
:Str
type str = DropSubStr<'12121212121','1'>;函数类型的重新构造
在函数类型上添加一个参数
type AppendArgument<Func extends Function, Arg> =
Func extends (...args: infer Args)=>infer ResultType ?
(...args: [...Args, Arg])=>ResultType
:never
type fu = AppendArgument<()=>string,number>;索引类型重新构造
把索引类型的Key变成大写
type UppercaseKey<Obj extends Object> = {
[Key in keyof Obj as Uppercase<Key & string>]:Obj[Key]
}
type obj = UppercaseKey<{
name: string
}>Record
typescript内置了Record，用来创建索引类型。
type Record<K extends keyof any, T> = {
[P in K]: T;
};我们可以使用Record修改上面将Key变成大写的代码
type UppercaseKey<Obj extends Record<string,any>> = {
[Key in keyof Obj as Uppercase<Key & string>]:Obj[Key]
}
type obj = UppercaseKey<{
name: string
}>将索引转换成只读
type ToReadonly<T> = {
readonly [Key in keyof T]: T[Key];
}
type obj = ToReadonly<{
name: '1'
}>;给索引添加可选修饰符
type ToPartial<T> = {
readonly [Key in keyof T]?: T[Key];
}
type obj = ToPartial<{
name: '1'
}>;去掉只读修饰符
type ToMutable<T> = {
-readonly [Key in keyof T]: T[Key];
}
type obj = ToMutable<{
readonly name: '1'
}>;去掉可选修饰符
type ToRequired<T> = {
[Key in keyof T]-?: T[Key];
}
type obj = ToRequired<{
name?: '1'
}>;对索引类型做过滤
type FilterByValueType<Obj extends Record<string,any>,valueType> = {
[Key in keyof Obj as Obj[Key] extends valueType ? Key : never] : Obj[Key];
}
type obj = FilterByValueType<{
name: string
un: undefined
nu: number
},undefined|number>;