I want to make a static array in a javascript class, for this I do:
var Manager = (function () {
function Manager() {
var ubications = new ArrayList();
this.ubicationsArray = function () {
return(ubication);
};
}
Manager.prototype.addUbication = function (ubication) {
Manager.ubicationsArray().add(ubication);
};
Manager.prototype.getUbication = function (index) {
return Manager.ubicationsArray().get(index);
};
Manager.prototype.sizeOfUbications = function () {
return Manager.ubicationsArray().size();
};
return Manager;
}());
Manager["__class"] = "Manager";
Where ubications is the static array and the function ubicationsArray is the public function to acces the array.
I try to use this code with:
var ubication = new Ubication(123,456);
var manager = new Manager();
manager.addUbication(ubication);
alert(manager.sizeOfUbications());
But I got this error:
Uncaught TypeError: Manager.ubicationsArray is not a function
How is the correct way to use static arrays in a javascript code?
Currently, JavaScript can only do privacy with respect to function scope.
function Manager () {
}
Manager.prototype = (function (){
var ubications = [];
return {
addUbication: function (u) {
ubications.push(u);
},
getUbication: function (index) {
return ubications[index];
},
sizeOfUbications: function () {
return ubications.length;
}
};
})();
Inside your constructor function, this.ubicationsArray assigns a property to the instance of the object, not the constructor itself.
Perhaps you want something like this:
function Manager() {
}
var ubications = new ArrayList();
Manager.ubicationsArray = function () {
return(ubication);
};
Note that this property isn't really "private". This would be more-private:
var Manager = (function () {
function Manager() {
}
var ubications = new ArrayList();
Manager.prototype.addUbication = function (ubication) {
ubications.add(ubication);
};
Manager.prototype.getUbication = function (index) {
return ubications.get(index);
};
Manager.prototype.sizeOfUbications = function () {
return ubications.size();
};
return Manager;
}());
Manager["__class"] = "Manager";
Related
I've been trying to learn Javascript. This is my code - I'm trying to implement a singleton - but for some reason, I get the error setMessage is not a function in the line firstInstance.setMessage("Message");. I have no idea what I'm doing wrong - any help would be greatly appreciated.
`
var mySingleton = (function () {
var instance;
var message;
function getInstance() {
if (!instance) instance = new Object();
return instance;
}
function setM (newMessage) {
message = newMessage;
return;
}
function getM() {
return message;
}
return {
createInstance:getInstance,
setMessage:setM,
getMessage:getM
}
})();
var firstInstance = mySingleton.createInstance();
var secondInstance = mySingleton.createInstance();
//set messages
firstInstance.setMessage("Message");
console.log(firstInstance.getMessage());
console.log(secondInstance.getMessage());
//change messages
secondInstance.setMessage("New");
console.log(firstInstance.getMessage());
console.log(secondInstance.getMessage());`
The setMessage and getMessage need to be on the instance you create, not in the object returned with the createInstance:
var mySingleton = (function() {
let instance;
let message;
function createInstance() {
if (!instance) instance = { setMessage, getMessage };
return instance;
}
function setMessage(newMessage) {
message = newMessage;
}
function getMessage() {
return message;
}
return { createInstance }
})();
var firstInstance = mySingleton.createInstance();
var secondInstance = mySingleton.createInstance();
firstInstance.setMessage("Message");
console.log(firstInstance.getMessage());
console.log(secondInstance.getMessage());
secondInstance.setMessage("New");
console.log(firstInstance.getMessage());
console.log(secondInstance.getMessage())
This doesn't work.
var genericClickHandler = function () {
this.handlers = [];
if (console && console.log) {
console.log("this:", this);
console.log("event:", event);
}
};
genericClickHandler.addHandler = function (handlerSpec) {
this.handlers.push(handlerSpec);
return this;
};
genericClickHandler.executeHandler = function (handlerName) {
for (var i = 0; i < this.handlers.length; i++) {
if (handlerName === this.handlers[i][0]) {
this.handlers[i][1]();
}
}
return this;
};
It doesn't work because the addHandler can't see the this.handlers in genericClickHandler.
Anyway what I'm after is function that gets defined once, but has methods and properties. I want to be able to use the function with Google Maps like this:
heatmap.addListener("click", genericClickHandler)
circle.addListener("click", genericClickHandler)
polygons.addListener("click", genericClickHandler)
So in the first instance, it only reports the this and event object. However, I then want to write code which extends the genericClickHandler dynamically so that it can implement map-object-specific behaviour.
Here's an example of what I meant using an object rather than a function.
var genericClickHandler = {
handlers: []
};
genericClickHandler.addHandler = function (name, fn) {
this.handlers.push([name, fn]);
return this;
};
genericClickHandler.executeHandler = function (name) {
for (var i = 0, l = this.handlers.length; i < l; i++) {
if (this.handlers[i][0] === name) this.handlers[i][1]();
}
};
genericClickHandler.addHandler('click', function () {
console.log('hi');
});
genericClickHandler.addHandler('click', function () {
console.log('hallo again');
});
genericClickHandler.executeHandler('click'); // hi... hallo again
DEMO
if you want to create an object, here you can see 2 ways to do the same thing, javascript got multiple way to write the same things.
var genericClickHandler = function()
{
this.handlers = [];
this.addHandler = function (handlerSpec)
{
this.handlers.push(handlerSpec);
return this;
},
this.executeHandler = function (handlerName)
{
this.handlers[handlerName]();
return this;
}
};
//sample:
var tmp = new genericClickHandler();
console.log(tmp.handlers);
console.log(tmp.addHandler("TEST"));
Another way to write the same object, but more optimised : prototype will be stored once for each object
var genericClickHandler = function(){}
genericClickHandler.prototype =
{
handlers:[],
addHandler : function (handlerSpec)
{
this.handlers.push(handlerSpec);
return this;
},
executeHandler : function (handlerName)
{
this.handlers[handlerName]();
return this;
}
}
//sample:
var tmp = new genericClickHandler();
console.log(tmp.handlers);
console.log(tmp.addHandler("TEST"));
I have following javascript code
function MyFunc () {
var add = function () {
return "Hello from add";
};
var div = function () {
return "Hello from div";
};
var funcCall = function (obj) {
if (!obj) {
throw new Error("no Objects are passed");
}
return obj.fName();
};
return {
func: function (obj) {
funcCall(obj);
}
};
}
var lol = new MyFunc();
When lol.func({fName: add}); is passed it should invoke the function private function add or when lol.func({fName: div}); is passed it should invoke the private div function. What i have tried does not work. How can i achieve this.
DEMO
In this case it's better to store your inner function in the object so you can easily access this with variable name. So if you define a function "map"
var methods = {
add: add,
div: div
};
you will be able to call it with methods[obj.fName]();.
Full code:
function MyFunc() {
var add = function () {
return "Hello from add";
};
var div = function () {
return "Hello from div";
};
var methods = {
add: add,
div: div
};
var funcCall = function (obj) {
if (!obj) {
throw new Error("no Objects are passed");
}
return methods[obj.fName]();
};
return {
func: function (obj) {
return funcCall(obj);
}
};
}
var lol = new MyFunc();
console.log( lol.func({fName: 'add'}) );
When you pass lol.func({fName: add}) add is resolved in the scope of evaluating this code, not in the scope of MyFunc. You have to either define it in that scope like:
function MyFunc () {
var add = function () {
return "Hello from add";
};
var div = function () {
return "Hello from div";
};
var funcCall = function (obj) {
if (!obj) {
throw new Error("no Objects are passed");
}
return obj.fName();
};
return {
add: add,
div: div,
func: function (obj) {
funcCall(obj);
}
};
}
var lol = new MyFunc();
lol.func({fName: lol.add});
Or use eval.
Trying to implement singleton pattern in javascript following some tutorials. Just wondering if there is any other way to implement the same ?
var singleton = (function(){
var getInstance; //private variable
var createWidget = function(){
var todayDate = new Date(); //private
var addCSS = function(){
console.log('THis is my css function');
};
var getDropDownData = function(){
console.log('This is my getDropDownData function');
};
return {
getDropDownData : getDropDownData,
addCSS: addCSS
};
};
return {
getInstance: function(){
if(!getInstance) {
getInstance = createWidget();
}
return getInstance;
}
};
})();
var obj = singleton.getInstance();
Implementing it by running anonymous function at onLoad and assiging it to some variable. Can we implement it without running this function at onLoad ?
You could always write a function to abstract away the boilerplate for writing singletons. For example this is what I would do:
function singleton(prototype) {
var instance = null;
return {
getInstance: function () {
if (instance === null) {
var Instance = prototype.init || function () {};
Instance.prototype = prototype;
instance = new Instance;
} return instance;
}
};
}
Then you can use this function to create singletons as follows:
var Widget = singleton({
init: function () {
var todayDate = new Date; // private
},
addCSS: function () {
console.log("This is my addCSS function.");
},
getDropDownData: function () {
console.log("This is my getDropDownData function.");
}
});
After that you use the singleton as you normally would:
var widget = Widget.getInstance();
Hope that helps.
i'm practicing with Javascript Inheritance, my first try is following code:
var base_class = function()
{
var _data = null;
function _get() {
return _data;
}
this.get = function() {
return _get();
}
this.init = function(data) {
_data = data;
}
}
var new_class = function() {
base_class.call(this);
var _data = 'test';
function _getData() {
return this.get();
}
this.getDataOther = function() {
return _getData();
}
this.getData = function() {
return this.get();
}
this.init(_data);
}
new_class.prototype = base_class.prototype;
var instance = new new_class();
alert(instance.getData());
alert(instance.getDataOther());
to that point i am really happy with my solution, but there is one problem
that i dont get resolved.
the "getDataOther" method don`t return the stored data from the base class,
because i cannot access the public "get" class from the protected "_getData" method in the new_class.
How can i get that running ?
Thanks in advance.
Ps.: Please excuse my poor English
If you comment out the this.init function (which overwrites the base_class _data field) and make the new_class's getData function just return _data, you should be able to get distinct variables.
var base_class = function()
{
var _data = null;
function _get() {
return _data;
}
this.get = function() {
return _get();
}
this.init = function(data) {
_data = data;
}
}
var new_class = function() {
var self = this; //Some browsers require a separate this reference for
//internal functions.
//http://book.mixu.net/ch4.html
base_class.call(this);
var _data = 'test';
function _getData() {
return self.get();
}
this.getDataOther = function() {
return _getData();
}
this.getData = function() {
return _data; //Changed this line to just return data
//Before, it did the same thing as _getData()
}
//this.init(_data); //Commented out this function (it was changing the base_class' data)
}
new_class.prototype = base_class.prototype;
var instance = new new_class();
alert(instance.getData());
alert(instance.getDataOther());
Your english is fine by the way :)