stream

var fs = require('fs')
var data = ''
var readerStream = fs.createReadStream('./index.html')
readerStream.setEncoding('utf-8')
readerStream.on('data', (chunk) => {
    data += chunk
})
readerStream.on('end', (chunk) => {
    console.log(data)
})
var writerStream = fs.createWriteStream('./zmh.html')
writerStream.write(data, 'utf-8');
writerStream.end();
writerStream.on('finish', () => {
    console.log('写入完成')
})