node工具之nodemon

原文链接：学习 nodemon 的实现原理

安装依赖

npm i chokidar

创建启动文件

//index.js
const chokidar = require('chokidar'), {spawn} = require('child_process');
//要启动和监听的目标文件
const targetFile = 'main.js'

function debounce(fn, delay) {
  var id;
  return function() {
    clearTimeout(id);
    id = setTimeout(function(){
      fn()
    }, delay)
  }
}

var childProcess;
function start() {
  childProcess && childProcess.kill();
  console.log('start again');
  childProcess = spawn('node', [targetFile], {
    stdio:[process.stdin, process.stdout, process.stderr]
  })
}

chokidar.watch(targetFile).on('all', function(evt, path){
  console.log(evt, path);
  debounce(start, 500)()
})

创建被监听页面

//main.js
const {createServer} = require('http'), url = require('url')
//创建一个服务器，监听8000端口
createServer(function(req, res){
  try {
    const pathname = url.parse(req.url).pathname;
    console.log('pathname: ', pathname, ['/', '/index'].includes(pathname));
    res.writeHead(200, {'Content-Type': 'text/html;charset=utf-8;'});
    var resContent = 'index.html'
    pathname && ['/', '/index'].includes(pathname) && (resContent = 'hello node')
    res.write(resContent)
    res.end()
  } catch (error) {
    console.error(error);
  }
}).listen(8000)

console.log(`http server is listening 0.0.0.0:8000`);

效果

小知识

1. child_process 子进程
   提供了衍生子进程的能力，主要是child_precess.spawn()函数
2. child_process.spawn(command[, args][, options])
3. chokidar
   小而高效的文件监听器