10969-medium-integer

Back 

type Integer<T extends number> = number extends T
  ? never
  : `${T}` extends `${any}.${any}`
  ? never
  : T;

Solution by sunupupup #33468 

// your answers
type Integer<T extends number> = number extends T
  ? never
  : `${T}` extends `${infer Int extends number}.${infer Float}`
  ? never
  : T;

Solution by pea-sys #33369 

type Integer<T> = T extends number 
  ? `${T}` extends `${number}.${number}`
    ? never
    : T
  : never```

Solution by keyurparalkar #32722 

// your answers

type Integer<T> = number extends T
  ? never
  : T extends number
  ? `${T}` extends `${number}.${number}`
    ? never
    : T
  : never;

Solution by kerolossamir165 #29444 

type Integer<T extends number> = number extends T
  ? never
  : `${T}` extends `${infer Int extends number}.${infer Float}`
  ? never
  : T;

Solution by DoubleWoodLin #28863 

type RemoveZero<T extends string> = T extends `${infer Num}0`
  ? RemoveZero<Num>
  : T;

type Integer<
  T extends number,
  U extends string = RemoveZero<`${T}`>
> = U extends `${infer Int extends number}.${infer Float}`
  ? Float extends ""
    ? Int
    : never
  : U extends `${infer Num extends number}`
  ? number extends Num
    ? never
    : Num
  : never;

Solution by DoubleWoodLin #28861 

type Integer<T extends number> = `${T}` extends `${string}.${string}`
  ? never
  : number extends T
  ? never
  : T;

Solution by DoGukKim #28449

判断是不是整数有两个关键，浮点数整数，正整数

  1. number extends T ? never : ...：如果 T 是 number 类型或 number 类型的子类型，按照上面的讨论，通常情况下会进入 : ... 这个分支。如果 T 是 string 类型，会匹配到 never。

  2. ${T}：将 T 转换为模板文字类型。如果 T 是 number 类型，这将把数字转换为字符串。例如，如果 T 是 42，${T} 将会是字符串 "42"。

  3. ${T} extends ${string}.${string} ? never : T:接下来检查 ${T}（数字变为字符串的结果，如"42"）是否符合 ${string}.${string} 的格式。这是一个字符串，其中包含一个或多个字符、一个点号，后跟一个或多个字符。简单地说，就是用来检查 T 是否包含一个小数点。

type Integer<T extends string | number> = number extends T 
  ? never
  : `${T}` extends `${string}.${string}` 
    ? never 
    : T

Solution by linjunc #28261 

type Integer<T extends any> = T extends Number ? T : never;

Solution by 20yuteo #27782 

type Integer<T extends number> = number extends T ? 
  never : 
  `${T}` extends `${string}.${string}` ? 
    never : 
    T

Solution by jjswifty #27386 

type Integer<T extends number> = number extends T ? never : `${T}` extends `${number}.${number}` ? never : T

Solution by smileboyi #27254 

// your answers
type Integer<T extends number> = number extends T
  ? never
  : `${T}` extends `${number}.${'' | number}`
  ? never
  : T

Solution by studymachiney #24691 

type Integer<T extends number> = number extends T ? never : `${T}` extends `${any}.${any}` ? never : T;

// fantastic way
// type Integer<T extends number> = `${T}` extends `${bigint}` ? T : never

Solution by E-uler #24552 

type Integer<T extends number> = number extends T
? never
: `${T}` extends `${number}.${'' | number}`
  ? never
  : T

Solution by NeylonR #24372 

type Integer<T extends number> = number extends T
  ? never
  // 1.0 => 1 ref: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-8.html#improved-inference-for-infer-types-in-template-string-types
  : `${T}` extends `${infer R extends number}`
  // Filter decimal
  ? `${T}` extends `${infer I extends number}.${infer D extends number}`
    ? never
    : R
  : never;

Solution by nia3y #23372 

// your answers 
type Integer<T> = `${T & number}` extends `${0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9}` ? 1 : never

Solution by snakeUni #23331 

// 你的答案
type Integer<T> = `${T & number}` extends `${0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9}` ? 1 : never

Solution by jxhhdx #22755 

type Integer<T extends number> = `${T}` extends `${bigint}` ? T : never

Playground

Solution by teamchong #22533 

type Integer<T extends number> =
  number extends T
    ? never
    : `${T}` extends `${infer _A}.${infer _B}`
      ? never
      : T

Solution by drylint #22126 

type Integer<T extends number> = number extends T
  ? never
  : `${T}` extends `${infer I}.${infer R}`
    ? never
    : T

Solution by jgjgill #21579 

type Integer<T> = 
  T extends number
    ? `${T}` extends `${infer F}.${infer L}`
      ? L extends 0 ? F : never
      : number extends T ? never : T
    : never;

Solution by ivbrajkovic #21528 

type Integer<T extends number> = `${T}` extends `${infer F}.${infer L}`
  ? L extends 0
    ? F
    : never
  : number extends T ? never : T

Solution by milletlovemouse #21447 

type Integer<T extends number> = `${T}` extends `${infer I}.${infer Last}` ? never: number extends T? never: T;

Solution by BruceYuj #21293 

type Integer<T> = number extends T ? never : T extends number
    ? `${T}` extends `${number}.${string}`
    ? never
    : T
    : never;

Solution by venusliang #20888 

type Integer<T extends number> =
  `${T}` extends `${infer A}.${infer B extends 0}`
    ? A
    : `${T}` extends `${infer G extends number}${infer P}`
    ? T extends G
      ? number extends G
        ? never
        : G
      : never
    : never;

Solution by so11y #20830 

// your answers
type Integer<T extends number> = `${T}` extends `${infer F}.${infer G}` ? never : number extends T ? never : T

Solution by YqxLzx #20250 

// your answers
type Integer<T> = T extends number | string
  ? `${T}` extends `${string}.${string}`
    ? never
    : `${T}`
  : never;

Solution by fengjinlong #20108 

type Integer<T extends number> = 
  number extends T
    ? never
    : `${T}` extends `${number}` 
      ? `${T}` extends `${any}.${any}`
        ? never
        : T
      : never

type Integer<T extends number> = `${T}` extends `${bigint}` ? T : never

Solution by zhaoyao91 #19875 

// your answers

type isLegalNumber<T extends number, S = `${T}}`> = S extends `${string}.${infer r}` ? r extends '0' ? true : false : true

type Integer<T extends number> = [number] extends [T] ? never : isLegalNumber<T> extends true ? T : never

Solution by ccctw-ma #19667 

type Integer<T extends number> = T extends number ? `${T}` extends `${infer F}.${infer L}` ? L extends 0 ? T : never : number extends T ? never : T : never;

Solution by sromic #19083