Add waitProperty helper.

Author: ZhukV

CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+v1.0.7
+------
+
+* Add helper `waitProperty`.
+
 v1.0.6
 ------
 

package-lock.json

@@ -1,6 +1,6 @@
 {
     "name": "@fivelab/web-utils",
-    "version": "1.0.5",
+    "version": "1.0.7",
     "private": false,
     "type": "module",
     "description": "The helpers for easy manipulate with dom.",

package.json

@@ -1,4 +1,5 @@
 export * from './config';
 export * from './observable';
 export * from './path';
-export * from './time';
+export * from './time';
+export * from './wait';

src/core/index.ts

@@ -0,0 +1,33 @@
+export type WaitPropertyOptions = {
+    timeout?: number;   // ms, default 5000
+    interval?: number;  // ms, default 50
+};
+
+export function waitProperty<T = unknown>(obj: object, key: PropertyKey, options: WaitPropertyOptions = {}): Promise<T> {
+    const {
+        timeout = 5000,
+        interval = 50,
+    } = options;
+
+    return new Promise((resolve, reject) => {
+        const start = Date.now();
+
+        const check = () => {
+            if (Object.prototype.hasOwnProperty.call(obj, key)) {
+                resolve((obj as any)[key] as T); // eslint-disable-line @typescript-eslint/no-explicit-any
+
+                return;
+            }
+
+            if (Date.now() - start >= timeout) {
+                reject(new Error(`Property "${String(key)}" was not defined within ${timeout}ms.`));
+
+                return;
+            }
+
+            setTimeout(check, interval);
+        };
+
+        check();
+    });
+}

src/core/wait.ts

@@ -0,0 +1,69 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { waitProperty } from '../../src/core';
+
+describe('wait property', () => {
+    beforeEach(() => {
+        vi.useFakeTimers();
+    });
+
+    it('resolves immediately if property already exists', async () => {
+        const obj = {foo: 123};
+
+        const promise = waitProperty<number>(obj, 'foo');
+
+        await expect(promise).resolves.toBe(123);
+    });
+
+    it('resolves when property appears later', async () => {
+        const obj: Record<string, unknown> = {};
+
+        const promise = waitProperty<string>(obj, 'bar', {
+            interval: 10,
+            timeout: 100,
+        });
+
+        setTimeout(() => {
+            obj.bar = 'hello';
+        }, 30);
+
+        vi.advanceTimersByTime(30);
+        await Promise.resolve();
+
+        await expect(promise).resolves.toBe('hello');
+    });
+
+    it('rejects on timeout', async () => {
+        const obj = {};
+
+        const promise = waitProperty(obj, 'missing', {
+            interval: 10,
+            timeout: 50,
+        });
+
+        vi.advanceTimersByTime(60);
+        await Promise.resolve();
+
+        await expect(promise).rejects.toThrow(
+            'Property "missing" was not defined within 50ms'
+        );
+    });
+
+    it('resolves multiple waiters when property appears', async () => {
+        const obj: Record<string, unknown> = {};
+
+        const p1 = waitProperty<string>(obj, 'shared', {interval: 10});
+        const p2 = waitProperty<string>(obj, 'shared', {interval: 10});
+
+        setTimeout(() => {
+            obj.shared = 'ok';
+        }, 20);
+
+        vi.advanceTimersByTime(20);
+        await Promise.resolve();
+
+        const [v1, v2] = await Promise.all([p1, p2]);
+
+        expect(v1).toBe('ok');
+        expect(v2).toBe('ok');
+    });
+});

tests/core/wait.test.ts

@@ -1,6 +1,7 @@
-import { afterEach, beforeEach, Mock, vi } from 'vitest';
+import { afterEach, vi } from 'vitest';
 
 afterEach(() => {
     vi.clearAllMocks();
     vi.resetAllMocks();
+    vi.useRealTimers();
 });