Naming this in nested functions

gistfile1.md

tl;dr

If you must nest functions in a way that requires access to multiple this', alias outer this to something meaningful - describe the value it's holding. Treat this as the invisible first argument.

In general though, avoiding the situation (nested functions and frivolous use of this) will frequently produce clearer results.

Naming this in nested functions

I was accidentally included in a discussion on how to best name this in nested functions in JavaScript. +1's were given to this suggestion of using _this.

Giving style advice on naming nested this without a meaningful context isn't too helpful in my opinion. Examples below have been altered to have at least some context, although a completely contrived and stupid one.

Assume this setup:

var morgan = new Person("Morgan");

Bad

morgan.logger = function() {
  var self = this;
  return function() {
    console.log(self);
  };
};

Bad

morgan.logger = function() {
  var that = this;
  return function() {
    console.log(that);
  };
};

Bad (still no good in my opinion)

morgan.logger = function() {
  var _this = this;
  return function() {
    console.log(_this);
  };
};

Meaningful name: Better

morgan.logger = function() {
  var person = this;
  return function() {
    console.log(person);
  };
};

Another more realistic example

Function.prototype.throttle = function (ms) {
    var fn = this;
    var timer;
    return function () {
        clearTimeout(timer);
        var args = [].slice.call(arguments);
        timer = setTimeout(function () {
            fn.apply(this, args);
        }, ms || 100);
    };
};

var throttled = myFunc.throttle(50);
throttled("Hey there!");

In the above example, "fn" is way superior to "_this". Still, the following example would be even better:

function throttle(fn, ms) {
    var timer;
    return function () {
        clearTimeout(timer);
        var args = [].slice.call(arguments);
        timer = setTimeout(function () {
            fn.apply(this, args);
        }, ms || 100);
    };
};

var throttled = throttle(myFunc, 50);
throttled("Hey");
throttled("Hey there!");

In summary

See tl;dr ;)