Why do we need "var self = this" in classes in Javascript?

javascript, json, knockout.js

Solution

There's no reason why you can't use `this` directly there (and I would say it would be better for readability if you did).

However, the `var self = this;` is often needed in situations like the following (basically, any asynchronous action like event binding, AJAX handlers etc, where the resolution of `this` is deferred until it equals something else);

function SeatReservation(name, initialMeal) {
    var self = this;
    self.name = name;
    self.meal = ko.observable(initialMeal);

    setTimeout(function () {
        alert(self.name); // otherwise, this is window; use self to keep a reference to the "SeatReservation" instance.
    }, 100);
}

Problem

Why can't we directly use `this` instead of `self` in the following example? ``` function SeatReservation(name, initialMeal) { var self = this; self.name = name; self.meal = ko.observable(initialMeal); } ``` After responses, I've learned: Yes, there is no need if there is no context switch in class. But I will use this approach as "convention" although there is no need.

Original source