Run child processes in Nodejs in queue (in my example the Astro build process)

index.js

const { spawn } = require('child_process');

let queue = ['A', 'B'];
let currentlyProcessing = false;

const addToQueueContinueWithNext = (newItem) => {
	queue.push(newItem);
	checkQueueAndStartIfIdle();
}

const removeFirstItemFromQueueContinueWithNext = () => {
	queue.shift();
	checkQueueAndStartIfIdle();
}

const checkQueueAndStartIfIdle = () => {
	if(currentlyProcessing === false && queue.length > 0){
		const nextProcess = queue[0];
		startProcessing(nextProcess);
	}else{
		console.log('- Queue is empty or already processing. Queue:', currentlyProcessing, ' Currently processing:',queue)
	}
}

const startProcessing = async(processId) => {
	console.log('---------------------');
	currentlyProcessing = true;
	await childProcess(processId);
	currentlyProcessing = false;
	removeFirstItemFromQueueContinueWithNext();
}

const childProcess = async(processId) => {
	console.log('- Run Astro build process for', processId);
	const childProcess = spawn('npm', ['run', 'astro-build']);

	childProcess.stdout.on('data', (data) => {
	  console.log(`  - Log: ${data}`);
	});

	childProcess.stderr.on('data', (data) => {
	  console.error(`  - Error: ${data}`);
	});

	const exitCode = await new Promise( (resolve, reject) => {
        childProcess.on('close', resolve);
    });

	console.log(`  - Done: Child process exited with code ${exitCode}`);
	return true;
}

addToQueueContinueWithNext('C');
// checkQueueAndStartIfIdle()