node.js - 在写入结果可用之前是否应该注册 `drain` 事件

Question

我有这段代码:

const file = fs.createWriteStream('./test.txt');
let written = true;

// handler is added before even an attempt to write is made
file.on('drain', function () {
    written = true;
    console.log('drained');
});

const interval = setInterval(function () {
    if (Date.now() - time > 10000) {
        clearInterval(interval);
    }

    if (written) {
        written = file.write(new Array(1000000).join('z'));
    }
}, 100);

我想知道是否有添加处理程序(即使尝试写入)的标准做法？

Answer 1

如果使用 file.on('drain') 监听器，您可以设置通用监听器来排出流的事件。注意:关闭可写流后，该监听器将被删除。

通常，该代码可以正常工作，但 Node.js 中最常见的做法是对每种内部缓冲区超出的情况使用 stream.once('drain') 处理程序。 Event: 'drain' 的 Node.js 文档中介绍了该方法。 :

function writeOneMillionTimes(writer, data, encoding, callback) {
    var i = 1000000;
    write();
    function write() {
        var ok = true;

        do {
            i -= 1;
            if (i === 0) {
                // last time!
                writer.write(data, encoding, callback);
            } else {
                // see if we should continue, or wait
                // don't pass the callback, because we're not done yet.
                ok = writer.write(data, encoding);
            }
        } while (i > 0 && ok);

        if (i > 0) {
            // had to stop early!
            // write some more once it drains
            writer.once('drain', write);
        }
    }
}