Javascript defineGetter

Question

var a = {}; 

a.__defineGetter__('test',function() {return 5;}); 

var i ="test";

Is there any other way I can execute the getter besides a[i] (while using var i to do it)

EDIT:

I was asking ways to use var i to do it. I'll explain the real problem a bit better.

I am using getters on my namespace object to load modules only when needed.

MyNameSpace.__defineGetter__('db',function(){MyNameSpace.loadModule('db');});

In this case I am trying to load all modules:

for (var i in MyNameSpace){
    MyNameSpace[i];
}

I use Google closure compiler on my code, and it reduces that loop above to:

for(var i in MyNameSpace);

No modules get loaded. I am trying to "trick" gcc into letting me load the modules.

casablanca · Accepted Answer · 2010-09-03 01:03:21Z

7

You can do either a.test or a['test'] - both will access the test property of a and hence call the getter.

Edit: Ah, I see exactly what you want now. What you're doing is a clever use of getters, but unfortunately getters and setters aren't part of the current JavaScript standard (they are in ECMAScript 5 which isn't widely supported yet). Google Closure Tools seems to assume that reading a variable can't have any side-effect, which is true in the current versions of JavaScript, so I see no way to get around that. You'll have to edit the output to insert that stuff back.

Also, this isn't related to your question, but I do hope you're doing an additional hasOwnProperty check within the for-in construct.

edited Sep 3, 2010 at 1:03

answered Sep 3, 2010 at 0:21

casablanca

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1 Comment

user113716 Over a year ago

OP seems to want to use the i variable. (while using var i to do it)

J.C. Inacio · Accepted Answer · 2011-05-25 18:10:27Z

4

I guess closure compiler optimizes out the code because it doesn't actually do anything but access the properties. this should work:

module = {}; // global
for (var i in MyNameSpace){
    module = MyNameSpace[i];
}

answered May 25, 2011 at 18:10

J.C. Inacio

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Comments

Chris Subagio · Accepted Answer · 2012-01-14 18:15:13Z

0

Looking at your module example, seems like you just want a little refactoring there.

var moduleNames = { 'db', 'input', 'etc' };

for ( var name in moduleNames ) {
  MyNameSpace.__defineGetter__(name,function(){MyNameSpace.loadModule(name);});
}

function loadAll() {
  for ( var name in moduleNames ) {
    MyNameSpace.loadModule(name);
  }
}

If the functions themselves are less trivial than that, then you similarly want to collect the functions into a handy dictionary ahead of time, then loop over those to create the getter, and loop again to create the load all function.

answered Jan 14, 2012 at 18:15

Chris Subagio

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