setInterval，setTimeout和Node.js中的回调函数

Question

I write an application in Node.js which are going to be engine like as simulator game fg. football match. I want to have "on-line broadcast" and for this reason I created functions like below. I wonder why my code doesn't work properly. What I'm expecting:

wait

wait

wait

wait

wait

something

wait

wait

wait

wait

wait

something

wait

etc.

but I don't have any idea what's wrong with my code, look at this:

getText: function() {
    console.log("something");
},
setDelay: function(callback) {
    var that = this;
    setTimeout(function() {
        callback();
    },5000);
},
play: function() {
    var that = this;
    setInterval(function(){
        console.log("wait");
        that.setDelay(that.getText);    
    },1000);
},

I'm getting something like this:

wait

wait

wait

wait

wait

something

wait

something

wait

something

etc.

any ideas will be appreciated.

Answer 1

It's because you're calling setDelay() every second:

getText: function() {
    console.log("something");
},
setDelay: function(callback) {
    var that = this;
    setTimeout(function () {
        callback();
    }, 5000);
},
play: function() {
    var that = this;
    setInterval(function () {
        console.log("wait");
        that.setDelay(that.getText); // << here
    }, 1000);
},

What happens:

1s -> setDelay() -> timeout1 is created
2s -> setDelay() -> timeout2 is created
3s -> setDelay() -> timeout3 is created
4s -> setDelay() -> timeout4 is created
5s -> setDelay() -> timeout5 is created
6s -> setDelay() -> timeout6 is created // timeout1's 5s are done, so it fires
7s -> setDelay() -> timeout7 is created // timeout2's 5s are done, so it fires
8s -> setDelay() -> timeout8 is created // timeout3's 5s are done, so it fires
and so on...

Answer 2

Inside of your play function, every second, you're running that.setDelay , which then waits five seconds before running console.log("something"); .

What you could do instead is have two setInterval 's running:

play: function() {
    var that = this;
    setInterval(function () {
        console.log("wait");
    }, 1000);
    setInterval(function () {
        that.getText();
    }, 5000);
},

This way, every second you'll get the output "wait", and every five seconds, the output "something".

Merry Christmas!

Answer 3

I would try to unpick the two intermingled timeouts/intervals and have just one that you clear/reset once you've reached the loop limit. It makes it a little easier to follow. Something like this:

function play(count) {
  var count = count || 1;
  var t;
  console.log(count);
  if (count !== 0 && count % 5 === 0) {
    clearTimeout(t);
    console.log('something');
    t = setTimeout(play, 5000, 1);
  } else {
    t = setTimeout(play, 1000, ++count);
  }
}

play();

DEMO

Or, in line with your own code:

var obj = {
  delay: 5000,
  timer: 1000,
  getText: function () {
    console.log('something');
  },
  play: function(count) {
    var count = count || 1;
    var t;
    if (count !== 0 && count % 5 === 0) {
      clearTimeout(t);
      this.getText();
      t = setTimeout(this.play.bind(this), this.delay, 1);
    } else {
      t = setTimeout(this.play.bind(this), this.timer, ++count);
    }
  }
}

obj.play();

DEMO