👍 Add isAllOf

Author: Milly

is.ts

@@ -255,9 +255,7 @@ export function isSymbol(x: unknown): x is symbol {
   return typeof x === "symbol";
 }
 
-export type OneOf<T> = T extends (infer U)[]
-  ? T extends Predicate<infer U>[] ? U : T
-  : T;
+export type OneOf<T> = T extends Predicate<infer U>[] ? U : never;
 
 /**
  * Return a type predicate function that returns `true` if the type of `x` is `OneOf<T>`.
@@ -279,6 +277,32 @@ export function isOneOf<T extends readonly Predicate<unknown>[]>(
   return (x: unknown): x is OneOf<T> => preds.some((pred) => pred(x));
 }
 
+type UnionToIntersection<U> =
+  (U extends unknown ? (k: U) => void : never) extends ((k: infer I) => void)
+    ? I
+    : never;
+export type AllOf<T> = UnionToIntersection<OneOf<T>>;
+
+/**
+ * Return a type predicate function that returns `true` if the type of `x` is `AllOf<T>`.
+ *
+ * ```ts
+ * import is from "./is.ts";
+ *
+ * const preds = [is.ObjectOf({ a: is.Number }), is.ObjectOf({ b: is.String })];
+ * const a: unknown = { a: 0, b: "a" };
+ * if (is.AllOf(preds)(a)) {
+ *  // a is narrowed to { a: number; b: string }
+ *  const _: { a: number; b: string } = a;
+ * }
+ * ```
+ */
+export function isAllOf<T extends readonly Predicate<unknown>[]>(
+  preds: T,
+): Predicate<AllOf<T>> {
+  return (x: unknown): x is AllOf<T> => preds.every((pred) => pred(x));
+}
+
 export type OptionalPredicate<T> = Predicate<T | undefined> & {
   optional: true;
 };
@@ -323,5 +347,6 @@ export default {
   Nullish: isNullish,
   Symbol: isSymbol,
   OneOf: isOneOf,
+  AllOf: isAllOf,
   OptionalOf: isOptionalOf,
 };

is_bench.ts

@@ -267,6 +267,27 @@ Deno.bench({
   },
 });
 
+const predsAll = [is.String, is.Number, is.Boolean] as const;
+Deno.bench({
+  name: "is.AllOf",
+  fn: () => {
+    const pred = is.AllOf(predsAll);
+    for (const c of cs) {
+      pred(c);
+    }
+  },
+});
+
+const isAllOfPred = is.AllOf(predsAll);
+Deno.bench({
+  name: "is.AllOf (pre)",
+  fn: () => {
+    for (const c of cs) {
+      isAllOfPred(c);
+    }
+  },
+});
+
 Deno.bench({
   name: "is.OptionalOf",
   fn: () => {

is_test.ts

@@ -7,6 +7,7 @@ import type {
   IsExact,
 } from "https://deno.land/std@0.192.0/testing/types.ts";
 import is, {
+  isAllOf,
   isArray,
   isArrayOf,
   isBigInt,
@@ -442,6 +443,45 @@ Deno.test("isOneOf<T>", async (t) => {
   });
 });
 
+Deno.test("isAllOf<T>", async (t) => {
+  await t.step("returns proper type predicate", () => {
+    const preds = [
+      is.ObjectOf({ a: is.Number }),
+      is.ObjectOf({ b: is.String }),
+    ];
+    const a: unknown = { a: 0, b: "a" };
+    if (isAllOf(preds)(a)) {
+      type _ = AssertTrue<IsExact<typeof a, { a: number; b: string }>>;
+    }
+  });
+  await t.step("returns true on all of T", () => {
+    const preds = [
+      is.ObjectOf({ a: is.Number }),
+      is.ObjectOf({ b: is.String }),
+    ];
+    assertEquals(isAllOf(preds)({ a: 0, b: "a" }), true);
+  });
+  await t.step("returns false on non of T", async (t) => {
+    const preds = [
+      is.ObjectOf({ a: is.Number }),
+      is.ObjectOf({ b: is.String }),
+    ];
+    assertEquals(
+      isAllOf(preds)({ a: 0, b: 0 }),
+      false,
+      "Some properties has wrong type",
+    );
+    assertEquals(
+      isAllOf(preds)({ a: 0 }),
+      false,
+      "Some properties does not exists",
+    );
+    await testWithExamples(t, isAllOf(preds), {
+      excludeExamples: ["record"],
+    });
+  });
+});
+
 Deno.test("isOptionalOf<T>", async (t) => {
   await t.step("returns proper type predicate", () => {
     const a: unknown = undefined;