Question

我正在向Nodejs服务器发送POST请求（使用Express）。在POST处理中，我需要从3个不同的文件中读取数据并将它们推送到3个数组中。但是，似乎res.end（）在读取完成之前发生。有人可以帮忙解决这个问题，这是我的过程功能。（response = [[]，[]，[]]）

app.post('/process_post', urlencodedParser, function(req, res) {

    var readMail = readline.createInterface({
        input : fs.createReadStream(path.join(process.cwd(), '/mail.txt'))
    });
    var readSubject1 = readline.createInterface({
        input : fs.createReadStream(path.join(process.cwd(), '/subject1.txt'))
    });
    var readSubject2 = readline.createInterface({
        input : fs.createReadStream(path.join(process.cwd(), '/subject2.txt'))
    });

        readMail.on('line', function(line) { 
            email.push(line);
        });
        readMail.on('close', function() {
            // resolve(email);
            console.log('finish mail');

        });
        readSubject1.on('line', function(line) { sub1.push(line) }).on('close', function() {
            console.log('finish subject1');
        });
        readSubject2.on('line', function(line) { sub2.push(line) }).on('close', function() {
            console.log('finish subject2');
        });


    var response = [email, sub1, sub2];
    res.end(JSON.stringify(response));
});

Answer 1

您必须使用异步进程。基本上，回调是许多nodejs方法的关键。我强烈建议你学习承诺，回调或像async这样的库。无论如何，我在您的代码中添加了promises。你应该在promise.all。

之后返回你的res.end函数

var p1 = new Promise((resolve, reject) => {
    readMail.on('line', function(line) {
        email.push(line);
    });
    readMail.on('error', function(error) {
        reject(error)
    });
    readMail.on('close', function() {
        resolve(email);
    });
});

var p2 = new Promise((resolve, reject) => {
    readSubject1.on('line', function(line) {
        sub1.push(line)
    }).on('close', function() {
        resolve(sub1);
    }).on('error', function(err) {
        reject(err);
    })
});

var p3 = new Promise((resolve, reject) => {
    readSubject2.on('line', function(line) {
        sub2.push(line)
    }).on('close', function() {
        resolve(sub2);
    }).on('error', function(err) {
        reject(err);
    })
});

Promise.all([p1, p2, p3])
    .then(values => {
        console.log('values [p1, p2, p3]');
        res.end(values);
    })
    .catch(err => {
        console.log(err);
    })

Nodejs中的同步读取线

1 个答案: