Introduction to lock-defer

The lock-defer package provides a powerful mechanism to manage asynchronous operations in a systematic and manageable way. By utilizing lock-defer, developers can streamline their code, handle errors gracefully, and ensure clean-up operations are performed. In this article, we will explore various APIs offered by lock-defer with dozens of useful examples and a sample application.

Getting Started with lock-defer

To start using lock-defer, you will need to install it via npm:

npm install lock-defer

Key API Functions

1. defer

The defer function allows you to schedule a function to be executed later.

const { defer } = require('lock-defer');

const deferred = defer(() => {
 console.log('Deferred function executed');
});
deferred();

2. lock

The lock function provides a locking mechanism to prevent multiple executions of a function simultaneously.

const { lock } = require('lock-defer');

const task = lock(async () => {
 console.log('Task started');
 await new Promise(r => setTimeout(r, 1000));
 console.log('Task finished');
});

task();
task(); // This will wait until the first task completes

3. withDeferred

The withDeferred function allows us to execute a function and ensures that all deferred functions are executed at the end.

const { withDeferred, defer } = require('lock-defer');

withDeferred(({defer}) => {
 defer(() => console.log('Cleanup operation'));
 console.log('Main operation');
});

4. Deferred Object

The Deferred object can be used to create and handle deferred operations.

const { Deferred } = require('lock-defer');

const deferred = new Deferred();

deferred.promise.then(() => {
 console.log('Promise resolved');
});

deferred.resolve();

Application Example

Let’s create a sample application using lock-defer to demonstrate its capabilities.

const { lock, defer, withDeferred } = require('lock-defer');

async function fetchData() {
 console.log('Fetching data...');
 return new Promise(resolve => setTimeout(() => resolve('Data'), 2000));
}

const performTask = lock(async () => {
 const data = await withDeferred(async ({defer}) => {
  const data = await fetchData();
  defer(() => console.log('Deferred cleanup after fetching data'));
  return data;
 });
 console.log('Data fetched:', data);
});

performTask();
performTask(); // Will wait until the first execution completes

In this example, we demonstrated the following:

• Using lock to manage concurrent tasks.
• Utilizing withDeferred to handle deferred operations and ensure clean-ups.
• Fetching data asynchronously while ensuring required clean-up actions.

By leveraging the power of lock-defer, you can write clean, manageable, and efficient asynchronous code in your applications.

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