Stateful Goroutines in JavaScript

In this example, we'll demonstrate how to manage state using asynchronous operations in JavaScript. This approach aligns with JavaScript's event-driven nature and asynchronous programming model.

```javascript
const crypto = require('crypto');

// These classes encapsulate read and write operations
class ReadOp {
    constructor(key) {
        this.key = key;
        this.promise = new Promise((resolve) => {
            this.resolve = resolve;
        });
    }
}

class WriteOp {
    constructor(key, val) {
        this.key = key;
        this.val = val;
        this.promise = new Promise((resolve) => {
            this.resolve = resolve;
        });
    }
}

// Main function to run our example
async function main() {
    let readOps = 0;
    let writeOps = 0;

    // Channels for read and write operations
    const reads = [];
    const writes = [];

    // This function simulates the state-owning goroutine
    async function stateManager() {
        const state = new Map();

        while (true) {
            if (reads.length > 0) {
                const read = reads.shift();
                read.resolve(state.get(read.key));
            } else if (writes.length > 0) {
                const write = writes.shift();
                state.set(write.key, write.val);
                write.resolve(true);
            } else {
                await new Promise(resolve => setTimeout(resolve, 0));
            }
        }
    }

    // Start the state manager
    stateManager();

    // Start 100 read operations
    for (let r = 0; r < 100; r++) {
        (async () => {
            while (true) {
                const read = new ReadOp(crypto.randomInt(5));
                reads.push(read);
                await read.promise;
                readOps++;
                await new Promise(resolve => setTimeout(resolve, 1));
            }
        })();
    }

    // Start 10 write operations
    for (let w = 0; w < 10; w++) {
        (async () => {
            while (true) {
                const write = new WriteOp(crypto.randomInt(5), crypto.randomInt(100));
                writes.push(write);
                await write.promise;
                writeOps++;
                await new Promise(resolve => setTimeout(resolve, 1));
            }
        })();
    }

    // Let the operations run for a second
    await new Promise(resolve => setTimeout(resolve, 1000));

    // Report the operation counts
    console.log("readOps:", readOps);
    console.log("writeOps:", writeOps);
}

main();

Running our program shows that the asynchronous state management example completes about 80,000 total operations.

$ node stateful-async.js
readOps: 71708
writeOps: 7177

This JavaScript approach uses asynchronous functions and Promises to simulate the behavior of goroutines. The stateManager function acts as the central goroutine that owns the state, while the read and write operations are performed by separate asynchronous functions.

The ReadOp and WriteOp classes encapsulate the operations and use Promises to provide a way for the operations to be resolved asynchronously.

This approach might be more complex than using a simple object with synchronous methods, but it can be useful in scenarios where you need to manage concurrent access to shared state in a non-blocking way, especially in event-driven environments like Node.js.

You should use whichever approach feels most natural and leads to the most understandable and correct program for your specific use case.

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Stateful Goroutines in JavaScript