javascript - 检查函数是否始终返回 bool 值

Question

我需要检查用户指定的谓词是否始终返回 bool 值。示例代码如下所示:

let isMostlyBoolean = function (aPredicate) {

return ( typeof aPredicate(undefined) === 'boolean' &&
    typeof aPredicate(null) === 'boolean' &&
    typeof aPredicate(false) === 'boolean' &&
    typeof aPredicate(Number.NaN) === 'boolean' &&
    typeof aPredicate(256) === 'boolean' &&
    typeof aPredicate("text") === 'boolean' &&
    typeof aPredicate('s') === 'boolean' &&
    typeof aPredicate(Math.sqrt) === 'boolean' &&
    typeof aPredicate(Object) === 'boolean' &&
    typeof aPredicate(['x', 'y', 'z']) === 'boolean'
);

}

有效。是否有更简洁和/或更有效的 aPredicate 检查方法？这里我们扫描所有可能的data types一一。

如 _.isFunction(a) vs. typeof a === 'function'? javascript 中所述讨论 typeof 应该是正确的选择。知道如何以更奇特和可读的方式做到这一点吗？

Edit: Note that the test above is a kind of fuzzy logic. Function name was changed accordingly. See @georg comments and more below.

给出测试代码:

let prediLess = (x) => x<2;
let predicate = (x) => x || (x<2);

console.log("isMostlyBoolean(prediLess): ", isMostlyBoolean(prediLess));
console.log("isMostlyBoolean(predicate): ", isMostlyBoolean(predicate));

console.log("\nprediLess(undefined): ", prediLess(undefined));
console.log("prediLess(1): ", prediLess(1));
console.log("prediLess(Object): ", prediLess(Object));

console.log("\npredicate(undefined): ", predicate(undefined));
console.log("predicate(1): ", predicate(1));
console.log("predicate(Object): ", predicate(Object));

控制台输出是:

returnsBoolean(prediLess):  true
returnsBoolean(predicate):  false

prediLess(undefined):  false
prediLess(1):  true
prediLess(Object):  false

predicate(undefined):  false
predicate(1):  1
predicate(Object):  function Object() { [native code] }

Answer 1

 [undefined, null, NaN, 0, 1, "", "a", [], [1], {}].every(el => typeof aPredicate(el) === "boolean");

只需将所有可能的值存储在一个数组中，然后迭代它并检查每个值是否适合。