Meteor.setTimeout超时后返回

Question

I have this switch case,

var res=null;
switch(case){
case "Delay":
        console.log("Start Delay");
        var timer = Meteor.setTimeout(function(){
            console.log("done Delay");
            res="sample";
        },15000);
        console.log("test Delay");
        break;
}
return res;

The code above will log "Start Delay" & "test Delay". Then it will start the timer. After 15000ms, it will log "done Delay". The problem here is the returning of res variable. Before the start of the timer, it already return res which is a null.

How can I return a variable after the timeout?

I also tried the suggested answer, this is my code for timeout and sleep function,

var timeout = function(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}
var sleep = async function(fn, ...args) {
    await timeout(3000);
    return fn(...args);
}

I changed my switch case,

var res=null;
switch(case){
case "Delay":
        console.log("Start Delay");
        sleep(function(){
            console.log("done Delay");
            res="sample";
        },15000);
        console.log("test Delay");
        break;
}
return res;

But still the res variable returned null instead of "sample".

Answer 1

Your switch statement is asynchronous and will not wait for your timeout to complete before returning your response.

You should make use of callback functions in this scenario. Here is a rough example of what you are possibly trying to achieve:

 var WorkWithResponse = function(response){
   console.log(response)
 }

var res=null;
var TestResponse = function(x, callback){

    switch(x){
    case "Delay":
            console.log("Start Delay");

            //This is the AngularJS $timeout service, 
            //replace with your own Meteor timeout method

            $timeout(function(){
              console.log('Delay over')
              res="Response Here";
              callback(res);
            },5000)
            console.log("test Delay");
            break;
    }
    return res;
}

TestResponse("Delay",WorkWithResponse)

Answer 2

I used fibers/future package from npm. This package allow functions to wait to its async call before returning a value.