Detecting the end of a method chaining

Question

I've been through a lot of posts over the web(and in SO) saying that it is not possible. However, I did the following code:

var a = {
	_sum: 0,
	_timer: null,
	_resetTimer: function() {
		if (this._timer) {
			window.clearTimeout(this._timer);
		}

		this._timer = window.setTimeout(this._endChain.bind(this), 0);
	},
	_endChain: function() {
		console.log(this._sum);
	},

	A: function() {
		this._resetTimer();
		this._sum+= 1;
		return this;
	},
	B: function() {
		this._resetTimer();
		this._sum+= 2;
		return this;
	}
};

a.A().B().B().A();

_{Demo in JsFiddle}

I want to know how problematic this can be, if this is not encouraged to be used.

Edit:

A negative point is: if you need anything that would be processed by _endChain you could not use return, only with a promise or another timeout outside the whole chain. Example.

Marc Rohloff · Accepted Answer · 2017-03-21 18:45:58Z

It's not problematic in the sense that _endChain will always be called after the whole chain. In fact you could simplify the code by only creating the timer once:

var a = {
  _timer: null,
  _resetTimer: function() {
    if (!this._timer)
  	  this._timer = window.setTimeout(this._endChain.bind(this), 0);
  },

But the problem will come with code that follows for example:

a.A().B().B().A();
DoMoreStuff();

Most developers would be surprised to find that the first call has not completed. I think the better solution would be to implement an end method which is what many libraries do:

let result = a.A().B().B().A().end();
DoMoreStuff();

Or a promise like method:

a.A().B().B().A().then( function(result) {
  DoMoreStuff();
});

So it could work in case of a lone method which the rest of the code doesn't depends on. — DontVoteMeDown
– DontVoteMeDown, Commented Mar 21, 2017 at 18:54

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