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| (function(exports) { | |
| function Universe() { | |
| this.partialAnswer = 21; | |
| } | |
| exports.Universe = Universe; | |
| // private methods | |
| var privatePrototype = { | |
| _computeAnswer: function() { | |
| return this.partialAnswer * 2; | |
| } | |
| }; | |
| // public API | |
| Universe.prototype = { | |
| getAnswer: function() { | |
| return privatePrototype._computeAnswer.call(this); | |
| } | |
| }; | |
| })(this); | |
| console.log(new Universe().getAnswer()); // 42 |
| (function(exports) { | |
| function Universe() { | |
| this.partialAnswer = 21; | |
| } | |
| exports.Universe = Universe; | |
| // private methods | |
| function _computeAnswer() { | |
| return this.partialAnswer * 2; | |
| } | |
| // public API | |
| Universe.prototype = { | |
| getAnswer: function() { | |
| return _computeAnswer.call(this); | |
| } | |
| }; | |
| })(this); | |
| console.log(new Universe().getAnswer()); // 42 |
is it really private ?
private1.js
console.log(privatePrototype._computeAnswer.call(new Universe)); // 42
@DavidBruant ok I understand what you mean, but I don't want private state here, just private methods (functions if you like it more), which if I'm correct don't carry state in these very examples.
But if I want to handle private state, I'd probably turn the private prototype in to a new constructor for each public instance to carry its own private proto. Hope it makes sense.
@fedir updated the gist to highlight the purpose
@DavidBruant ok now I get what you mean, if I create a new constructor for each public instance to carry its own private proto, it wouldn't be private anymore because publicly attached to the public API. Makes sense. Can't wait for ES6 to address this :)
Why You call it private ? Better to call it hidden, masked methods, as they could be executed directly.
private2.js
console.log(_computeAnswer.call(new Universe())); // 42
@fedir nope, hence the IIFE:
(function(exports) {
function Universe() {
this.partialAnswer = 21;
}
exports.Universe = Universe;
// private methods
function _computeAnswer() {
return this.partialAnswer * 2;
}
// public API
Universe.prototype = {
getAnswer: function() {
return _computeAnswer.call(this);
}
};
})(this);
console.log(new Universe().getAnswer()); // 42
console.log(_computeAnswer.call(new Universe())); // ReferenceError: _computeAnswer is not defined
BruanT avec un T ! (sinon, je reçois pas de notif ;-) )
This only works if the private method acts on public state.
@n1k0 On Twitter:
I'm not sure what you mean. How do you make per-instance private state in JavaScript? Please answer with code ;-)
Hint: it's not possible; hence symbols in ES6 (but I can't find one good reference resource on the topic :-/ ). The spec on this topic has been moving a lot. One of the most promising approach for private state is relationships in my opinion. A good share of TC39 disagrees apparently...