javascript is it possible to use a string to call a object function

Question

I have a generic function which can speak to multiple other functions in appropriate objects is it possible to use a string to call the appropriate function.

 var string = "save";

 var generic = (new function (string) { 

                string."alert()";


               return this;
               })




 var save = (new function (string) { 

    this.alert = (function () {

              alert("your document has been saved")                    

              return this         

              })

        return this 
          })

var notSaved = (new function (string) { 

    this.alert = (function () {

              alert("your document has not been saved")                    

              return this         

              })

        return this 
          })

I am using it for a far more complex set up but here is an example. Is this possible?

"Use a string to call the appropriate function"? Would putting your functions in nested objects work so you could call something like generic["save"]["alert"]()? — JustcallmeDrago
– JustcallmeDrago, Commented Nov 5, 2011 at 6:32
Note that you don't need new function (){} You can use just function (){} — Some Guy
– Some Guy, Commented Nov 5, 2011 at 6:35

Some Guy · Accepted Answer · 2011-11-05 06:30:11Z

1

Sure you can. Try something like this:

window[string].alert();

answered Nov 5, 2011 at 6:30

Some Guy

16.2k10 gold badges61 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

davidchambers · Accepted Answer · 2011-11-05 07:16:26Z

Looking at your code it's hard to tell what you're actually trying to achieve. Nonetheless, here are a few ideas that may be relevant.

First, let's make a couple of objects:

var rabbit = {
  name: 'Peter',
  hop: function () {
    return this.name + ' hopped!'
  },
  jump: function () {
    return this.name + ' jumped!'
  }
}

var hairy_maclary = {
  name: 'Hairy Maclary',
  jump: function () {
    return this.name + ' jumped over the fence!'
  }
}

Now, you could define a function which invokes the hop method on whichever object is passed to it:

function hop(object) {
  return object.hop()
}

hop(rabbit) // 'Peter hopped!'

I'm not sure why you'd do this rather than invoking hop directly, but perhaps you want to do extra stuff before or afterwards.

If you wanted to you could create a completely generic function which would invoke a given method on a given object:

function invokeMethod(object, method) {
  object[method]()
}

invokeMethod(hairy_maclary, 'jump') // 'Hairy Maclary jumped over the fence!'

This is a really strange thing to want to do, though. Perhaps you could provide more of an idea of what you're actually trying to do, since your example code is rather odd.

Tadeck · Accepted Answer · 2011-11-05 06:36:18Z

0

You can enclose your functions within some object so you can access by passing name of the property using some variable (in this case named string), eg. like that:

var string = 'notSaved';
var funcs = {};

funcs.save = new function(){
    this.alert = function(){
        alert('called save.alert()');
    };
    return this;
};

funcs.notSaved = new function(){
    this.alert = function(){
        alert('called notSaved.alert()');
    };
    return this;
};

funcs[string].alert();

See working example on jsfiddle.

If your variables are global (they should not), they are also automatically enclosed within window object, so you can call them also like that: window[string].alert(). This will not work for non-global functions (in this case my solution seems to be the only one not using eval()).

answered Nov 5, 2011 at 6:36

Tadeck

138k28 gold badges155 silver badges201 bronze badges

6 Comments

davidchambers Over a year ago

This seems odd to me. Why make things so convoluted? Wouldn't funcs.save = {alert: function(){ alert('called save.alert()') }} achieve the same thing but much more simply?

Tadeck Over a year ago

@davidchambers: " Why make things so convoluted? ": There are different ways to mimic class-like behaviour in JavaScript (by default, JavaScript does not have any " classes ") and OP followed one of these ways - I just followed the same way. From the article I referenced: " It might look a bit confusing if you're not used to it (...) it's an option, when you really want a constructor function that you'll use only once and there's no sense of giving it a name ". What do you think about that? Is it still worth downvoting?

Ryan Over a year ago

@Tadeck, in software engineering in general, when there are multiple ways to achieve the same thing, you always want to pick the least convoluted from a readability perspective. Other programmers might have to modify your code someday ;) And as we all know, JS gives you a ton of ways to express the same thing ;)

Tadeck Over a year ago

@Ryan: In software engineering I was taught that the best approach is to choose... best solution suited for specific task. And I believe you are not clairvoyant and do not really know why OP has chosen to use this solution. Your solution is useless in at least one case - when the OP wants to be able to define what happens when the object is constructed (in other words: when wants to define code for constructor). Do you agree?

Ryan Over a year ago

@Tadeck, I didn't say you should use different solutions; I said that if you have multiple ways to express the same thing, then use the more readable form (if it's not too much of a performance hit). In this particular case, there's no need to do any construction, because his alert functions are not making use of this in any meaningful way. He simply needs separate objects that have an alert function defined as a property of the object. Just have him do something like saved = { alert: function() {...} }. That's easier to read and it actually does the same thing as what you're doing.

|

ymutlu · Accepted Answer · 2011-11-05 06:37:14Z

-1

eval("alert('test');");

You can call functions with eval. Even you can declare functions.

eval("function test(){ alert("test");}");

test();

answered Nov 5, 2011 at 6:37

ymutlu

6,7394 gold badges38 silver badges48 bronze badges

1 Comment

davidchambers Over a year ago

I'd prefer to see answers which promote good programming practice. In some cases eval is necessary, but this is certainly not one of them.

Collectives™ on Stack Overflow

javascript is it possible to use a string to call a object function

4 Answers 4

Comments

Comments

6 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

6 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related