In a Google Script, call a function by its name, given its name in a string

Question

I have tried the code examples that I found here on the "stackoverfllow" site, related to calling a function from a string. They don't seem to work in a Google App Script. I receive an error to effect that "window" as an undefined object.

Here is the situation that I am trying to solve. I have a spreadsheet that is going to have many different sheets. Some of these sheets will have names that are known at the time I write the code. Other sheets will have names that are not known exactly at the time I write the code (e.g. based on dynamic data).

The current documentation tells me that the name of the "onEdit" event handler is "onEdit". Since thee name is unique, I conclude that there can only be one such routine with this name within a spreadsheet application.

Because of this situation (above) I would like reduce the complexity of my "onEdit" function. I would like to write the "onEdit" routine to do "dynamic" calls to sub-functions which use qualified names, based upon the name of the "sheet" in which the edit event occurred.

Here is a pseudo code example of the "onEdit" routine I want to right.

  function onEdit(src)
  {
     var act_sheet = src.getActiveSheet();
     var sheet_name = act_sheet.getName();
     var rtn_name = "onEdit_sheet_".sheet_name;

     if ( function_exists(rtn_name) )
     {
         window[rtn_name](srv)
     }
  }

I have actually tried similar code. In the google environment the "window" object is flagged as an unknown object.

Is there some other "object" name in the environment that I should be using? Is this possible within the Google Apps Script environment?

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In addition, I know that the "function_exists" routine is also a challenge to write. That will be my next question. I know about the "typeof" operation, it returns "string" when I code

      "if ( typeof rtn_name == function" ) .. "

Is there a way to test that a routine exists given a name contained in a string?

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I know I can use "static" names and hard code them in the "onEdit" routine. But I would like to write the routine once, and not have to modify it for each new spreadsheet that I write. In stead of writing very complicated "onEdit" routines, I want to concentrate on writing and testing "onEdit" functions for individual sheet's.

I understand Javascript within a browser environment. The Google apps script environment is more of a mystery to me. I find the documentation very very terse, and in need of fuller explanations. Any additional information about what objects exist in the Google apps script environment would be helpful.

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Of course my third step might be to write an "onEdit" routine that dispatches the correct sub-function based upon the current "range" associated with an Edit event.

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I am NEW to Google Apps Scripts. I am looking for a script solution. It probably can be done in "Java", but that is beyond the scope in which I want to code.

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I am also new to the "stackoverflow" environment. Much of it seems a mystery to me. (e.g. How do I specify which tags should be associated with this question? How do I know which tags are available to be assigned to this question? How do I limit my search to certain tags? - I am at the moment interested in "google apps scripts", when I select the "javascript" button in the right column it takes me into a javascript answers which may not apply to the google script environment. Found out how to "assign" tags below. How do I know which tags are available without just guessing?

All and any help is appreciated.

Answer 1

I know two ways to call the function using its name on a string in Apps Script.

function onEdit(e) {
  var func = 'test';
  this[func]();
  //eval(func+'()'); //msgBox and eval don't play nice together
  Browser.msgBox('finished');
}

function test() {
  Browser.msgBox('test');
}

Of course, when using the this approach, you should not be in another scope, e.g. from a function called using new. But this exact full code that I'm posting works fine.