Object.getPrototypeOf(this) === Point.prototype <=> this instanceof Point
And I don't understand your problem >_ < On Fri, Nov 11, 2011 at 8:11 PM, Axel Rauschmayer <[email protected]> wrote: > Having recently bitten by a mistyped property name (see code underneath > signature), I think I might prevent the extension of instances more often. > But what is the best way of doing so? > > Variant 1: prevents subtyping the constructor > > function Point(x, y) { > this.x = x; > this.y = y; > Object.seal(this); > } > > Variant 2: allows subtyping, not very pretty. > > function Point(x, y) { > this.x = x; > this.y = y; > if (Object.getPrototypeOf(this) === Point.prototype) { > Object.seal(this); > } > } > > > > -- > Dr. Axel Rauschmayer > [email protected] > > home: rauschma.de > twitter: twitter.com/rauschma > blog: 2ality.com > > > Buggy code: > > var action = function() { ... }; > var c = new CountDown(1, action); > c.dec(); // action is *not* executed! > > > function CountDown(counter, finalAction) { > this.counter = counter; > this.finalAction = finalAction; > // Important! finalAction must always be executed > this.maybeFire(); > } > CountDown.prototype.maybeFire = function () { > if (this.counter <= 0 && this.finalAction) { > this.finalAction(); > } > }; > CountDown.prototype.dec = function () { > this.conter--; // typo! > this.maybeFire(); > }; > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
