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Module

std/assert/assert_instance_of.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.import { AssertionError } from "./assertion_error.ts";
/** Any constructor */// deno-lint-ignore no-explicit-anyexport type AnyConstructor = new (...args: any[]) => any;/** Gets constructor type */export type GetConstructorType<T extends AnyConstructor> = T extends // deno-lint-ignore no-explicit-anynew (...args: any) => infer C ? C : never;
/** * Make an assertion that `obj` is an instance of `type`. * If not then throw. * * @example * ```ts * import { assertInstanceOf } from "https://deno.land/std@$STD_VERSION/assert/assert_instance_of.ts"; * * assertInstanceOf(new Date(), Date); // Doesn't throw * assertInstanceOf(new Date(), Number); // Throws * ``` */export function assertInstanceOf<T extends AnyConstructor>( actual: unknown, expectedType: T, msg = "",): asserts actual is GetConstructorType<T> { if (actual instanceof expectedType) return;
const msgSuffix = msg ? `: ${msg}` : "."; const expectedTypeStr = expectedType.name;
let actualTypeStr = ""; if (actual === null) { actualTypeStr = "null"; } else if (actual === undefined) { actualTypeStr = "undefined"; } else if (typeof actual === "object") { actualTypeStr = actual.constructor?.name ?? "Object"; } else { actualTypeStr = typeof actual; }
if (expectedTypeStr === actualTypeStr) { msg = `Expected object to be an instance of "${expectedTypeStr}"${msgSuffix}`; } else if (actualTypeStr === "function") { msg = `Expected object to be an instance of "${expectedTypeStr}" but was not an instanced object${msgSuffix}`; } else { msg = `Expected object to be an instance of "${expectedTypeStr}" but was "${actualTypeStr}"${msgSuffix}`; }
throw new AssertionError(msg);}