类的JavaScript实例

Question

Let's say I have a function:

function Control(value){
    var self=this;
    self.param1=value;
    self.param2=value.text;
}

Is it possible to get all instances created by that function in JavaScript?

Answer 1

Without modifying the class, there is little you can do. If you can modify it, simply keep a reference of each instance you construct:

function Control(value){
    Control.instances = Control.instances || [];
    Control.instances.push(this);

    var self=this;
    self.param1=value;
    self.param2=value.text;
}

// In case you are worried about garbage collection
Control.prototype.destroy = function() {
    var index = Control.instances.indexOf(this);
    Control.instances.splice(index, 1);
}


// Usage:
var x = new Control();
var y = new Control();
// do stuff with x and y
console.log('There are ' + Control.instances.length + ' instances of Control');
// all done with x and y
x.destroy();
x = null;
y.destroy();
y = null;
// no more references to the two instances, they can be garbage collected

Be warned though, you will prevent the garbage collector from freeing the memory of any instance you don't call destroy() on.

Answer 2

I used something similar in one of my projects because i needed to call a method for all the instances...

function Person(firstname, lastname) {
    var self = this; // For reference to "this" 
    this.firstname = firstname;
    this.lastname = lastname;


    document.addEventListener( "event/person", function( event ) {
        var params = event.detail.params;
        Person.prototype[ params.method ].call(self);

       // Take params:   params.params => ["param1", "param2", "param3"]
    });
}


Person.prototype.toString = function() {
    console.log("Firstname: " + this.firstname + " Lastname: " + this.lastname);  
};


Person.prototype.callAll = function( params ) {
    document.dispatchEvent( new CustomEvent( "event/person", {
        detail: {
            "params": params   
        }
    }));
};


var a = new Person("Gabriel", "Gatu");
var b = new Person("Marco", "Giovannini");


Person.prototype.callAll({
    method: "toString",
    params: ["param1", "param2", "param3"]
});

It uses the listeners to communicate between a simple method and the constructor class, also allows you to call whatever method you want contained in the prototype of the class, passing parameters, if necessary...

ps Sorry for the bad english... :)

Answer 3

Just store it in a global array. Would be similar to some static pattern.

var controls = [] ; //Global array

function Control(value){
    var self = this;
    self.param1=value;
    self.param2=value.text;

   controls.push(self);
}

Answer 4

As @Ian suggested in his comment you can do it this way:

// global are bad though!
var controlInstances = [];

function Control(value){
    // track instances
    controlInstances.push(this)
    this.param1 = value;
    thsi.param2 = value.text;
}

Answer 5

I used something similar in one of my projects because i needed to call a method for all the instances...

function Person(firstname, lastname) {
    var self = this; // For reference to "this" 
    this.firstname = firstname;
    this.lastname = lastname;


    document.addEventListener( "event/person", function( event ) {
        var params = event.detail.params;
        Person.prototype[ params.method ].call(self);

       // Take params:   params.params => ["param1", "param2", "param3"]
    });
}


Person.prototype.toString = function() {
    console.log("Firstname: " + this.firstname + " Lastname: " + this.lastname);  
};


Person.prototype.callAll = function( params ) {
    document.dispatchEvent( new CustomEvent( "event/person", {
        detail: {
            "params": params   
        }
    }));
};


var a = new Person("Gabriel", "Gatu");
var b = new Person("Marco", "Giovannini");


Person.prototype.callAll({
    method: "toString",
    params: ["param1", "param2", "param3"]
});

It uses the listeners to communicate between a simple method and the constructor class, also allows you to call whatever method you want contained in the prototype of the class, passing parameters, if necessary...

ps Sorry for the bad english... :) See ya !

Answer 6

No.

The fact that you can only touch objects that you have explicit references to is part of JavaScript security model *.

* That security model is not applicable in JavaScript in cases of global objects.

Answer 7

var foo = new Control('bar');
console.log(foo.param1);