typescript - 如何在Typescript中指定数字的最小-最大范围？

Question

我有一个属性可以接收 0 到 256 之间的数字。如何在 typescript 中键入这样的范围？

function foo(threshold:number){
//do stuff
}

Answer 1

如果您只想在运行时检查它:

@Pluto 函数的更简单版本:

function foo(threshold: number): boolean {
    return 0 <= threshold && threshold <= 256;
}

如果您希望对其进行类型检查:

灵感来自这篇博文: https://basarat.gitbook.io/typescript/main-1/nominaltyping .

Typescript Playground link

enum SmallIntBrand { _ = "" }
type SmallInt = SmallIntBrand & number;

function isSmallInt(n: number): n is SmallInt {
    return Number.isInteger(n) &&
        0 <= n &&
        n <= 255;
}

const a = 434424;
const b = 25;

function requiresSmallInt(n: SmallInt) {
    console.log("Received number: " + n);
}

// Neither of these compile, for none of them
// have checked the variable with 'isSmallInt'.
//requiresSmallInt(a);
//requiresSmallInt(b);

if (isSmallInt(a)) {
    requiresSmallInt(a);
}

if (isSmallInt(b)) {
    requiresSmallInt(b);
}