Static variables in JavaScript

Static variables in JavaScript

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How can I create static variables in Javascript?


If you come from a class-based, statically typed object-oriented language (like Java, C++ or C#) I assume that you are trying to create a variable or method associated to a "type" but not to an instance.

An example using a "classical" approach, with constructor functions maybe could help you to catch the concepts of basic OO JavaScript:

function MyClass () { // constructor function
  var privateVariable = "foo";  // Private variable 

  this.publicVariable = "bar";  // Public variable 

  this.privilegedMethod = function () {  // Public Method
    alert(privateVariable);
  };
}

// Instance method will be available to all instances but only load once in memory 
MyClass.prototype.publicMethod = function () {    
  alert(this.publicVariable);
};

// Static variable shared by all instances
MyClass.staticProperty = "baz";

var myInstance = new MyClass();

staticProperty is defined in the MyClass object (which is a function) and has nothing to do with its created instances, JavaScript treats functions as first-class objects, so being an object, you can assign properties to a function.

Static variables in JavaScript, If you come from a class-based, statically typed object-oriented language (like Java, C++ or C#) I assume that you are trying to create a variable or method  There may be times when a static variable is needed in a Javascript function; static variables maintain their value between function calls and are tidier than using a global variable because they cannot be modified outside of the function. Example. The easiest way to explain how to do this is with an example.


You might take advantage of the fact that JS functions are also objects -- which means they can have properties.

For instance, quoting the example given on the (now vanished) article Static variables in Javascript:

function countMyself() {
    // Check to see if the counter has been initialized
    if ( typeof countMyself.counter == 'undefined' ) {
        // It has not... perform the initialization
        countMyself.counter = 0;
    }

    // Do something stupid to indicate the value
    alert(++countMyself.counter);
}

If you call that function several time, you'll see the counter is being incremented.

And this is probably a much better solution than poluting the global namespace with a global variable.

And here is another possible solution, based on a closure : Trick to use static variables in javascript :

var uniqueID = (function() {
   var id = 0; // This is the private persistent value
   // The outer function returns a nested function that has access
   // to the persistent value.  It is this nested function we're storing
   // in the variable uniqueID above.
   return function() { return id++; };  // Return and increment
})(); // Invoke the outer function after defining it.

Which gets you the same kind of result -- except, this time, the incremented value is returned, instead of displayed.

How to create static variables in JavaScript, Consider object Foo: [code js] var Foo = function(a) { this.x = a; }; Foo.y = 'static'; var z = 'global'; [/code] Foo has an instance variable named x. By definition this  Static method calls are made directly on the class and are not callable on instances of the class. Static methods are often used to create utility functions. Calling static methods From another static method. In order to call a static method within another static method of the same class, you can use the this keyword.


You do it through an IIFE (immediately invoked function expression):

var incr = (function () {
    var i = 1;

    return function () {
        return i++;
    }
})();

incr(); // returns 1
incr(); // returns 2

What is difference between private variable, public variable and , or method acts somewhat like a globally accessible function or variable. Simply import the class, and you can read the same value from anywhere else in the program. It's usually not advisable to rely on global variables as they can lead to spaghetti code, but that's not to say that they can't be used. Unlike these programming languages, JavaScript doesn’t support static variables. It doesn’t provide static keywords. But using a small tip, we can implement function static variables in JavaScript and use them for our purposes. Note: If you just get started with JavaScript, check out the collection of best free resources to learn JavaScript.


you can use arguments.callee to store "static" variables (this is useful in anonymous function too):

function () {
  arguments.callee.myStaticVar = arguments.callee.myStaticVar || 1;
  arguments.callee.myStaticVar++;
  alert(arguments.callee.myStaticVar);
}

AS3 101: Quick Tip – When to Use Static Properties and Methods, In programming languages like C, C++, static variables are variables that maintain their value between function calls. Unlike these  Questions: How can I create static variables in Javascript? Answers: If you come from a class-based, strongly typed object-oriented language (like Java, C++ or C#) I assume that you are trying to create a variable or method associated to a “type” but not to an instance.


Javascript Static Method vs Instance Method, staticMethod() call is the class constructor User itself (the “object before dot” rule). Usually, static methods are used to implement functions that  Consider object Foo: [code js] var Foo = function(a) { this.x = a; }; Foo.y = 'static'; var z = 'global'; [/code] Foo has an instance variable named x.


static, How to create Static Variables in Javascript ? Solution 1: If we come from a class-​based, strongly typed object-oriented language (like  What are static variable in Java, and what are they for? A static variable is one that's associated with a class, not objects of that class. Let's take a look at an example.


Create And Use Static Variables In JavaScript – Deluxe Blog Tips, Static methods in JavaScript : In the following example ShowCount() is a static method. Notice Duration: 10:02 Posted: Feb 7, 2015 Craig Buckler examines the proposed class fields feature of JavaScript, which aim to deliver simpler constructors with private and static members.


Static properties and methods, Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, Python, Bootstrap, Java  JavaScript Data Types. JavaScript variables can hold numbers like 100 and text values like "John Doe". In programming, text values are called text strings. JavaScript can handle many types of data, but for now, just think of numbers and strings. Strings are written inside double or single quotes. Numbers are written without quotes.