I'm stuck with a problem using javascript...
I want to declare a private variable in a class that can't be used from its sublclass...what I've tried is:
function Person(){
var _name
this.setName = function(name){
_name = name
}
this.getName = function(){
return _name
}
}
function GreetingPerson(){
var self = this;
self.sayHello = function(){
console.log(self.getName() + ': "Hello!"');
}
}
GreetingPerson.prototype = new Person()
GreetingPerson.prototype.contructor = GreetingPerson;
var manuel = new GreetingPerson()
manuel.setName('Manuel');
manuel.sayHello();
var world = new GreetingPerson()
world.setName('World');
world.sayHello();
manuel.sayHello();
console.log(manuel.name)
In this way the name variable is private, but it is also static, so the last wo sayHello method calls, will write the same output.
I've tried also changing the Person class in this way:
function Person(){
this.setName = function(name){
this.name = name
}
this.getName = function(){
return this.name
}
}
But in this way it is not longer private.
What is the correct way to achieve it?
EDIT: Using something like #teddybeard says, you can get it too:
function Person(){
var _name;
this.setName = function(name){
_name = name;
};
this.getName = function(){
return _name;
};
return this;
}
function GreetingPerson(){
Person.call(this);
this.sayHello = function(){
console.log(this.getName() + ': "Hello!"');
};
return this;
}
GreetingPerson.prototype = new Person();
GreetingPerson.prototype.constructor = GreetingPerson;
var manuel = new GreetingPerson();
manuel.setName('Manuel');
manuel.sayHello();
var world = new GreetingPerson();
world.setName('World');
world.sayHello();
manuel.sayHello();
console.log(manuel._name);
But I'm not pretty sure if this is actually ok. The problem is that if you don't do something like Person.call(this); inside the constructor of GreetingPerson, you will not create a new instance of Person and it will always use the same _name value.
Check out Eloquent Javascript if you have time. I think this code should work for your purposes of inheritance.
function Person() {
var _name
this.setName = function(name) {
_name = name
}
this.getName = function() {
return _name
}
}
function GreetingPerson() {
Person.call(this);
this.sayHello = function() {
console.log(this.getName() + ': "Hello!"');
}
}
// taken from Eloquent Javascript
function clone(object) {
function OneShotConstructor() {}
OneShotConstructor.prototype = object;
return new OneShotConstructor();
}
GreetingPerson.prototype = clone(Person.prototype);
GreetingPerson.prototype.contructor = GreetingPerson;
var manuel = new GreetingPerson()
manuel.setName('Manuel');
manuel.sayHello();
var world = new GreetingPerson()
world.setName('World');
world.sayHello();
manuel.sayHello();
console.log(manuel.name);
Related
I am trying to make a constructor function. Then I am trying to use its prototype and printing "Peter". But it is showing an error.
function main(){
var func1 = function(){
this.name = "Peter";
this.age = 27;
this.class = "10";
}
func1.prototype.printName = function(){
console.log(this.name);
}
return func1;
}
var a = main();
a.printName();
You are assigning the constructor function func1 to a, not an instance of func1. Only instances of func1 have a printName method. At some point you need to call new func1() or new a(). E.g. you could do return new func1(); instead of return func1;.
Have a look at the following, simplified example.
var func1 = function() {
this.name = "Peter";
this.age = 27;
this.class = "10";
}
func1.prototype.printName = function() {
console.log(this.name);
}
var a = new func1();
a.printName();
I recommend to read eloquentjavascript.net - The Secret Life of Objects.
How do you access the this object from another object instance?
var containerObj = {
Person: function(name){
this.name = name;
}
}
containerObj.Person.prototype.Bag = function(color){
this.color = color;
}
containerObj.Person.prototype.Bag.getOwnerName(){
return name; //I would like to access the name property of this instance of Person
}
var me = new Person("Asif");
var myBag = new me.Bag("black");
myBag.getOwnerName()// Want the method to return Asif
Don't put the constructor on the prototype of another class. Use a factory pattern:
function Person(name) {
this.name = name;
}
Person.prototype.makeBag = function(color) {
return new Bag(color, this);
};
function Bag(color, owner) {
this.color = color;
this.owner = owner;
}
Bag.prototype.getOwnerName = function() {
return this.owner.name;
};
var me = new Person("Asif");
var myBag = me.makeBag("black");
myBag.getOwnerName() // "Asif"
Related patterns to deal with this problem: Prototype for private sub-methods, Javascript - Is it a bad idea to use function constructors within closures?
I have a function that is similar to each other. How can I make declaring a function easier without duplicating
function constructor (name, numLegs) {
this.name = name;
this.numLegs = numLegs;
}
function Animal(name, numLegs) {
this.name = name;
this.numLegs = numLegs;
}
Animal.prototype.sayName = function() {
console.log("Hi my name is " + this.name);
};
// create a Penguin constructor here
function Penguin(name, numLegs){
this.name=name;
this.numLegs = numLegs;
}
// create a sayName method for Penguins here
Penguin.prototype.sayName = function() {
console.log("Hi my name is " + this.name);
};
// our test code
var theCaptain = new Penguin("Captain Cook", 2);
theCaptain.sayName();
You were almost there.
// create a Penguin constructor here
function Penguin(name, numLegs){
Animal.call(this, name, numLegs);
};
// Reuse the prototype chain
Penguin.prototype = Object.create(Animal.prototype);
Penguin.prototype.constructor = Penguin;
I'm reading about OPP js and while going over an example and was wondering if in:
function Person(name){
this.name = name;
}
Person.prototype.sayName = function(){
var tempName = this.name;
var saySomething = function(){
console.log(tempName);
}
//return saySomething();
}
var person1 = new Person('chris');
is theres a way to fire the saySomething method from the constructor.
eg.
person1.sayName().saySomething() //which doesnt work obviously
Returning an object when sayName will work:
function Person(name) {
this.name = name;
}
Person.prototype.sayName = function() {
var tempName = this.name;
return {
saySomething: function() {
console.log(tempName);
}
};
};
var person1 = new Person('chris');
person1.sayName().saySomething(); // logs 'chris'
I made a object to keep my functions became singleton, using that, i made sample methods to call and communicate each other.. but i don't get any appropriate results..
any one correct me, the singleton the way i defined here...
my sample codes:
var obj = window[obj] || {}; //singleton
obj.nameIt = function(name){
this.name = name;
this.getName = function(){
return this.name;
}
}
obj.sayIt = function(name){
this.name = name; var that = this;
this.sayHello = function(){
console.log("say" + this.name);
that.getName();//how to get result from nameIt?
}
}
var x = obj.nameIt("af");
console.log(x.getName());//says "undefined" - how to call it?
var y = obj.sayIt("xy");
console.log(y.sayHello());//says "undefined" - how to call it?
jsfiddle here
Your code does not return anything.
obj.nameIt = function(name){
this.name = name;
this.getName = function(){
return this.name;
}
return this;
}
obj.sayIt = function(name){
this.name = name; var that = this;
this.sayHello = function(){
console.log("say" + this.name);
return that.getName();
}
return this;
}