使用javascript异步，直到停止执行库

Question

I'm using libraries I didn't write and can't modify to do the following:

libx.on('something', function(x){
  liby.next_var(function(y,z){
    dance(x,y,z);
  })
})

Unfortunately, I don't want to dance all night. I want to make it possible to stop the execution of dance when a user clicks a button.

I tried to do this with the async library's until function:

var async = require('async');
var dancing = true;

async.until(function(){
  return !dancing;
},function(cb){
  libx.on('something', function(x){
    liby.next_var(function(y,z){
      dance(x,y,z);
    })
  })
},function(){
  console.log("dance() will no longer be called");
});

$('#stop').on('click', function(){
  // want to stop libx and liby calls
  dancing = false;
});

Keeping in mind I can't modify the signature of the on method for libx, or the next_var method of liby, how can I control and stop the callbacks to these methods from firing?

Answer 1

Your usage of async.until is fine, the issue is that you're registering an event handler so every time 'something' happens, you're going to dance. (Sounds fun!)

In this case, you don't even need to use async :

libx.on('something', function (x) {
  liby.next_var(function (y, z) {
    dance(x, y, z);
  })
})

$('#stop').on('click', function () {
  libx.removeListener('something', function () {
    console.log("dance() will no longer be called");
  });
});

The event listener is registered immediately and then, when you click on stop , the listener is removed and you won't be dancing when 'something' happens again.

---

Alright, with a better understanding of the problem at hand, you were actually really close to the solution.

var async = require('async');
var dancing = true;

function danceUntil (x, y, z) {
  async.until(function () {
    return !dancing;
  }, function (cb) {
    dance(x, y, z);
    cb();
  }, function () {
    console.log("dance() will no longer be called");
  });
}

libx.on('something', function (x) {
  liby.next_var(function (y, z) {
    danceUntil(x, y, z);
  })
})

$('#stop').on('click', function () {
  dancing = false;
});