Introduction to `lazy-cache`

`lazy-cache` is a powerful Node.js module designed to defer the execution of heavy computations or IO-bound tasks until they are needed. By lazily loading these operations, you can significantly improve the startup performance of your applications. The library provides numerous APIs to efficiently manage lazy-loading.

Useful API Examples

Basic Usage

Here is a simple example demonstrating the basic usage of `lazy-cache`:

  const lazy = require('lazy-cache')(require);
  lazy('fs');

  // Using the deferred fs module
  lazy.fs.readFile('example.txt', 'utf8', (err, data) => {
    if (err) throw err;
    console.log(data);
  });

Using Custom Names

You can also assign a custom name to the lazily required module:

  const lazy = require('lazy-cache')(require);
  lazy('chalk', 'colorize');

  // Using the deferred chalk module with custom name
  console.log(lazy.colorize.green('Hello, world!'));

Lazy Loading a List of Modules

For loading multiple modules at once, you can use:

  const lazy = require('lazy-cache')(require);
  lazy('express');
  lazy('mongoose');
  lazy('body-parser');

  // Using the deferred modules
  const app = lazy.express();
  const mongoose = lazy.mongoose;
  const bodyParser = lazy['body-parser'];

  // Sample application setup
  app.use(bodyParser.json());
  mongoose.connect('mongodb://localhost/test', {useNewUrlParser: true, useUnifiedTopology: true});

Lazy Initialization

For expensive operations like database connections, you might want to defer initialization until the moment of use:

  const lazy = require('lazy-cache')(require);
  lazy('pg', 'pgClient');

  async function queryDatabase() {
    const client = new lazy.pgClient.Client({
      connectionString: 'postgresql://username:password@localhost:5432/mydb'
    });
    await client.connect();
    const res = await client.query('SELECT NOW()');
    await client.end();
    console.log(res.rows[0]);
  }

  queryDatabase();

Complete Application Example

Let’s put together a complete app that uses several `lazy-cache` APIs:

  const lazy = require('lazy-cache')(require);
  lazy('express');
  lazy('mongoose');
  lazy('body-parser');
  lazy('chalk', 'colorize');

  const app = lazy.express();
  const mongoose = lazy.mongoose;

  // Middleware
  app.use(lazy['body-parser'].json());

  // Database setup
  mongoose.connect('mongodb://localhost/myapp', { useNewUrlParser: true, useUnifiedTopology: true })
    .then(() => {
      console.log(lazy.colorize.green('Database connected successfully'));
    })
    .catch(err => {
      console.error(lazy.colorize.red('Database connection error:'), err);
    });

  // Sample route
  app.get('/', (req, res) => {
    res.send('Hello World!');
  });

  // Start server
  app.listen(3000, () => {
    console.log(lazy.colorize.blue('Server is running on port 3000'));
  });

In this example, we’ve set up a basic Express server, connected to a MongoDB database, and used `chalk` to colorize our console logs.

By using `lazy-cache`, we ensure that modules are only loaded when needed, thus optimizing the performance and startup time of our application.

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