Return a type predicate function that returns true if the type of x satisfies Record<K, T>.

To enhance performance, users are advised to cache the return value of this function and mitigate the creation cost.

import { is } from "@core/unknownutil";

const isMyType = is.RecordOf(is.Number);
const a: unknown = {"a": 0, "b": 1};
if (isMyType(a)) {
  // a is narrowed to Record<PropertyKey, number>
  const _: Record<PropertyKey, number> = a;
}

With predicate function for keys:

import { is } from "@core/unknownutil";

const isMyType = is.RecordOf(is.Number, is.String);
const a: unknown = {"a": 0, "b": 1};
if (isMyType(a)) {
  // a is narrowed to Record<string, number>
  const _: Record<string, number> = a;
}