Get object property name

[aj_nsc]

It seems like there must be a simple way to do thing but I can't think of it.

I have a simple debugger that looks like this:

levels = {
  'none' : 0,
  'message' : 1,
  'notice' : 2,
  'warning' : 3,
  'error' : 4
};

app.log = function(level,msg) {
  console.log('??? : '+msg);
}

//the code to fire the event
app.log(levels.warning,'A warning message');

Where the question marks are in the code above I want to say 'warning'....how do I do that?

I am open to the possibility that there is a more elegant way to code this is well.

[007Julien]

With a for in ?

app.log = function(level,msg) {var prop;
	for (prop in levels) if (levels[prop]==level) break;
	console.log(prop+' : '+msg);
}

[Jeff Mott]

You could also index the levels by number.

var levelsByNumber = {};
for (var levelName in levels) {
    var levelNumber = levels[levelName];

    levelsByNumber[levelNumber] = levelName;
}

Then you could write:

console.log(levelsByNumber[level]+' : '+msg);

Though, whether you ultimately use an index or a loop, unless there's more code we haven't seen, I'd say that representing levels using a number costs more than it saves. You'd be better off just passing a string.

[aj_nsc]

Both methods above will work, although I'd hate to run a for loop every time to get the property name. I ended up going Jeff's route in any case. I figured there'd be an easier way...

[007Julien]

That's obviously right. Both methods use a for in loop. There is perhaps not usefull to declare the variable levelNumber for each level ?

[bionoid]

Just the obvious suggestion:

app.log = function(level,msg) {
  console.log(['none', 'message', 'notice', 'warning', 'error'][level] + ' : '+msg);
}

... or using a different object:

levels = {
  none    : 'None',
  message : 'Message',
  notice  : 'Notice',
  warning : 'Warning',
  error   : 'Error'
}

app.log = function(level,msg) {
  console.log(level + ' : '+msg);
}

app.log(levels.warning, 'A warning message');