javascript - convert function into variable

Question

I googled a bit and it seems I either don't know what I'm asking or this isn't possible. I think it's probably the former.

If I have an object

obj = {
  func : function(){
    return 'hello';
  }
}

and I normally do alert(obj.func()) I of course get "hello"

But if I wanted to have obj.func be simply a variable, is that possible somehow? I won't ever pass parameters to the function, I just want to reference its return value as a plain variable like alert(obj.func) , not a function call.

Thanks.

Answer 1

Try this :

obj = {
  func : (function(){
    return 'hello';
  })()
}

Answer 2

Yes, thats easy!

var obj = {
  func :  'hello'
};

alert(obj.func);

see this working fiddle

if you want it to be a calculated value or sth. you can still let it be a function but callable like a simple property:

var obj = {
  func :  (function(){return 'hello';})()
};

Answer 3

What you are talking about is a getter : it is a function that works as a property. It is standard since javascript 1.8.5, which means older browser won't handle it.
The syntax is as follow, using your example :

obj = {
   get func() {  return "hello" ; }
};
// use like this :
console.log(obj.func);

Most likely you will want to define a setter also : this is also a function behaving like a property. The syntax will be :

obj = {
    get func()    { return this._innerText ; },
    set func(txt) { this._innerText = txt  ; },
    _innerText  : "hello" 
};

console.log(obj.func) ;   // output is hello
obj.func = "godd bye" ;
console.log(obj.func) ;   // output is good bye

Obviously, as often with simple example, this one is of no big use:

Let us see a degree to radian converter using a getter / setter :

 var Angle = {
        get degree ()        { return this._degree ; },
        set degree (dg)      { this._degree = dg   ; },
        get radian ()        { return 2*Math.PI*this.degree/360 ; },
        set radian (rd)      { this._degree = rd * 360 / (2*Math.PI) ; },
        _degree  : 0
} ;
// you can use :
Angle.radian = Math.PI / 2;
console.log ( Angle.degree );    // -->> output is 90
Angle.degree=45 ;
console.log(Angle.radian) ;      // --> output is 0.7853... which is PI/4

You might also have a look on Object.defineProperty, which allows to define both standard properties, and getters/setters, but with more option, especially the option to 'hide' a property, which allows it not to be enumerated.

For more information :
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/get https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/set https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/defineProperty

Answer 4

    var varFunc = function() { alert("hello"); }
    varFunc();