Websockets-在onmessage（）之外传递数据

Question

My WebExtension connects to a WebSockets server to retrieve data.

function foo(responseDetails){
    var ws = new WebSocket("ws://localhost:9876/");

    ws.onopen = function(event){
        // send some data to the server
        ws.send("some data");
    }

    ws.onmessage = function(event){
        // receive some data from the server
        data = event.data;
    }

    // how to access the data from here?
    if(data == 0)
        return {cancel:true}
    else
        return {cancel:false}
}

browser.webRequest.onBeforeRequest.addListener(
        foo, 
        {urls:["*//*/*"]},
        ["blocking"]
)

Whenever a request is completed, function foo() is called which opens a WebSocket to ws://localhost:9876 , sends a string, then receives data . The data determines whether or not the request will be blocked.

After reading through the answers here , I'm still confused. I'm not sure how to implement the callback while within function foo() .

Similar question but the answer is not what I'm looking for.

Answer 1

You can use promises for this exact use-case, something as follows should work:

function foo(responseDetails) {
  return new Promise(function(resolve) {
    var ws = new WebSocket("ws://localhost:9876/");

    ws.onopen = function(event) {
      // send some data to the server
      ws.send("some data");
    }

    ws.onmessage = function(event) {
      // receive some data from the server
      var data = event.data;
      if (data == 0) {
        resolve({
          cancel: true
        });
      } else {
        resolve({
          cancel: false
        })
      }
    }
  });
}

browser.webRequest.onBeforeRequest.addListener(
  foo, {
    urls: ["*//*/*"]
  }, ["blocking"]
)

More info can be found here