挣扎于js承诺，foreach承诺添加结果。

Posted 2023-02-24

谁能帮我解决这个问题，我想检索一下用webrtc发送了多少数据。但我无法理解这些承诺。

我需要遍历发送者列表，但对于每个发送者，我需要等待承诺，然后才能继续下一个发送者。

// Reset datacounter
Client.DataUsed = 0;

// Get senders (audio/video)
const senders = Client.WebcamConnection.getSenders();

// Iterate through senders
senders.forEach(sender => 
    // Get the stats then await the promise using then
    sender.getStats().then(stat => 
        // Iterate through raports of stat
        stat.forEach(report => 
            // Check if is the right raport
            if (report.type === 'outbound-rtp') 
                // Add the byte count to the datacounter
                Client.DataUsed += report.bytesSent + report.headerBytesSent;
            
        );
    );
);

// Do something with the Client.DataUsed

答案

就像你说的，你不能使用结果，直到所有的承诺被解决。你可以使用 Promise.all 伺机而动 *** 评论：

// Reset datacounter
Client.DataUsed = 0;

// Get senders (audio/video)
const senders = Client.WebcamConnection.getSenders();

// ***Create an array of promises, one for each sender, and pass it into
// `Promise.all`***
Promise.all(senders.map(sender => 
    // *** Return the promise created by `then` so `Promise.all` can
    // wait for it***
    // Get the stats then await the promise using then
    return sender.getStats().then(stat => 
        // Iterate through raports of stat
        stat.forEach(report => 
            // Check if is the right raport
            if (report.type === 'outbound-rtp') 
                // Add the byte count to the datacounter
                Client.DataUsed += report.bytesSent + report.headerBytesSent;
            
        );
    );
)
.then(() => 
    // Do something with the Client.DataUsed
)
.catch(error => 
    // Handle/report error
);