async-wait-until
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Waits until the given predicate function returns a truthy value, then resolves
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# async-wait-until
A lightweight, zero-dependency library for waiting asynchronously until a specific condition is met. Works in any JavaScript environment that supports [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise), including older Node.js versions and browsers (with polyfills if necessary).
[](https://npmjs.org/package/async-wait-until)
[](https://codeclimate.com/github/devlato/async-wait-until/maintainability)
## 📖 Detailed Documentation
For detailed documentation, visit [https://devlato.github.io/async-wait-until/](https://devlato.github.io/async-wait-until/)
## 🚀 Installation
Install using npm:
```sh
npm install async-wait-until
```
The library includes UMD, CommonJS, and ESM bundles, so you can use it in any environment.
```javascript
import { waitUntil } from 'async-wait-until';
// Example: Wait for an element to appear
await waitUntil(() => document.querySelector('#target') !== null);
```
## 🛠️ How to Use
### Basic Example: Wait for a DOM Element
```javascript
import { waitUntil } from 'async-wait-until';
const waitForElement = async () => {
// Wait for an element with the ID "target" to appear
const element = await waitUntil(() => document.querySelector('#target'), { timeout: 5000 });
console.log('Element found:', element);
};
waitForElement();
```
### Handling Timeouts
If the condition is not met within the timeout, a `TimeoutError` is thrown.
```javascript
import { waitUntil, TimeoutError } from 'async-wait-until';
const waitForElement = async () => {
try {
const element = await waitUntil(() => document.querySelector('#target'), { timeout: 5000 });
console.log('Element found:', element);
} catch (error) {
if (error instanceof TimeoutError) {
console.error('Timeout: Element not found');
} else {
console.error('Unexpected error:', error);
}
}
};
waitForElement();
```
## 📚 API
### `waitUntil(predicate, options)`
Waits for the `predicate` function to return a truthy value and resolves with that value.
**Parameters:**
| Name | Type | Required | Default | Description |
| --------------------------------- | ---------- | -------- | --------- | ------------------------------------------------------------------------------------ |
| `predicate` | `Function` | ✅ Yes | - | A function that returns a truthy value (or a Promise for one). |
| `options.timeout` | `number` | 🚫 No | `5000` ms | Maximum wait time before throwing `TimeoutError`. Use `WAIT_FOREVER` for no timeout. |
| `options.intervalBetweenAttempts` | `number` | 🚫 No | `50` ms | Interval between predicate evaluations. |
## 💡 Recipes
### Wait Indefinitely
Use `WAIT_FOREVER` to wait without a timeout:
```javascript
import { waitUntil, WAIT_FOREVER } from 'async-wait-until';
await waitUntil(() => someCondition, { timeout: WAIT_FOREVER });
```
### Adjust Retry Interval
Change how often the predicate is evaluated:
```javascript
await waitUntil(() => someCondition, { intervalBetweenAttempts: 1000 }); // Check every 1 second
```
## 🧪 Development and Testing
Contributions are welcome! To contribute:
1. Fork and clone the repository.
2. Install dependencies: `npm install`.
3. Use the following commands:
- **Run Tests:** `npm test`
- **Lint Code:** `npm run lint`
- **Format Code:** `npm run format`
- **Build Library:** `npm run build`
- **Generate Docs:** `npm run docs`
## 📝 Links
- [License](./LICENSE)
- [Detailed Documentation](https://devlato.github.io/async-wait-until/)
- [Changelog](./CHANGELOG.md) - Track version updates and changes
- [Contributing Guidelines](./CONTRIBUTING.md) - How to contribute to the project
- [Code of Conduct](./CODE_OF_CONDUCT.md) - Community standards and expectations