Using a string as a function name?

[frankvw]

Hi, all,

I am trying to do something like this:

var functionName = "theFunc";
functionName ();

Obviously the above syntax won't work - instead of theFunc() getting called, I get an error.

Is this possible at all, and if so, what is the correct way to do it?

All response appreciated!

// FvW

[astupidname]

var functionName = "theFunc";
window[functionName](); //invokes the function if it is a globally accessible function,
//which is actually a property of the window object
//To apply this technique to your own object, is the same:
var myObject = {
    name : 'fooObj',
    speak : function () {
        alert(this.name);
    }
};
 
var funcName = 'speak';
if (funcName in myObject && typeof myObject[funcName] == 'function') { //myObject has a property by the name of funcName's value, and it is a function
    myObject[funcName]();
}

[frankvw]

Thank you!!!!!!!!!!!! You saved my day... :-)

// FvW

[frankvw]

Thank you!!!!!!!!!!!! You saved my day... :-)

Well, maybe not, after all. Because what I am trying to do still won't work:

function ajaxRead (url, targetObj, updateHandler) {
  var xmlObj = new XMLHttpRequest ();
  xmlObj.onreadystatechange = function () {
    if (xmlObj.readyState == 4) {
      window [updateHandler (ajaxTarget, xmlObj.responseXML.getElementsByTagName('data')[0].firstChild.data)];
    }
  }
  xmlObj.open ('GET', url, true);
  xmlObj.send (null);
}

function ajaxUpdateObj (obj, data) {
  document.getElementById(obj).innerHTML = data;
}

When I call the above with something like

ajaxRead (url, target, 'ajaxUpdateObj')

(having previously set up url and target correctly, of course) I get an error message stating that 'updateHandler is not a function'. Any ideas?

// FvW

[astupidname]

You don't have the syntax right

window [updateHandler (ajaxTarget, xmlObj.responseXML.getElementsByTagName('data')[0].firstChild.data)];

Should be:

      window [updateHandler](ajaxTarget, xmlObj.responseXML.getElementsByTagName('data')[0].firstChild.data);

[frankvw]

You don't have the syntax right

Indeed, that turned out to be the problem. (My Javascript skills are still rather limited.)

I've got it working now. Onece agains my thanks!!

// FvW

[rnd me]

if you made your call ajaxRead (url, target, ajaxUpdateObj), then you can simply say:

 updateHandler(ajaxTarget, xmlObj.responseXML.getElementsByTagName('data')[0].firstChild.data);

there's no reason to pass strings like that; it just slows things down, demands globals, and makes your code harder to maintain.

[Declan1991]

Functions are variables like everything else, in this regard, JavaScript is like Lisp. Rnd me shows how to deal with them as variables.