const fs = require('fs');
    fs.readFile('1.txt', 'utf-8', (err, data) => {
        if (err) {
            console.log('文件读取失败');
        } else {
            fs.writeFile('2.txt', data + '呵呵呵', 'utf-8', (error) => {
                if (error) {
                    console.log('文件写入失败');
                }
            })
        }
    })