Function that gets it's properties

Question

How can I create a function where it gets it's property?
For example:

myfunc = function(){
    alert(this.a + ":" + this.b);
};
myfunc.a = 5;
myfunc.b = 6;

The results is 5:6

Answer 1

Try this:

myfunc = function(){
    alert(this.a + ":" + this.b);
};

myfunc.call({a: 5, b: 6});

When you use the call function, the first parameter is your function's this and the second parameter is your function. The call function just call you function and assign {a: 5, b: 6} to myfunc's this.

Answer 2

There are two ways. The first, is as others have mentioned is to name the parameters in your function delcaration:

function foo(a, b) {
    alert(a + ':' + b);
}

foo('hello', 'world'); // Output "hello:world"

---

Another way however is that a variable is available which contains all function parameters, called arguments.

function bar() {
    alert(arguments[0] + ':' + arguments[1]);
}

bar('hello', 'world'); // Output "hello:world"

It should be noted that while it looks like an array, the arguments variable is not an instance of the JavaScript Array object, the only Array property available to use with arguments is .length.

Answer 3

This could be done with a closure:

var myFunc = (function(a, b) {

  return function() {
    console.log(a + ":" + b);
  }

})(5, 6)

myFunc();

This can be expanded via prototype to create class like behaviour:

var myFunc = (function () {
    function myFunc(a, b) {
        if (a === void 0) { a = 5; }
        if (b === void 0) { b = 6; }
        this.a = a;
        this.b = b;
    }
    myFunc.prototype.log = function () {
        console.log(this.a + ":" + this.b);
    };
    return myFunc;
}());
var a = new myFunc();
a.log();
new myFunc().log();
new myFunc(1, 10).log();
//ACCESS ATTRIBUTE
console.log("ACCESSING", a.a);
//OVERWRITE ATTRIBUTE
a.a = 11;
//ACCESS ATTRIBUTE
console.log("ACCESSING", a.a);
a.log();