Javascript: Pass array as optional method args

Question

UPDATE: Here's my solution (inspired by accepted answer):

function log(msg, values) {
         if(config.log == true){
         msg = [msg];
         var args = msg.concat(values);
         console.log.apply( this, args );
         }
     }

UPDATE2: Even better solution:

 function log(msg) {
     if(config.log == true){
     msg = [msg];
     var values = Array.prototype.slice.call(arguments, 1);
     var args = msg.concat(values);
     console.log.apply( console, args );
     }
 }

You can call this version like so:

log("Hi my name is %s, and I like %s", "Dave", "Javascript");

Here's the original question:

console.log takes a string and replaces tokens with values, for example:

console.log("My name is %s, and I like %", 'Dave', 'Javascript')

would print:

My name is Dave, and I like Javascript

I'd like to wrap this inside a method like so:

function log(msg, values) {
  if(config.log == true){
    console.log(msg, values);
   }
 }

The 'values' arg might be a single value or several optional args. How can I accomplish this?

If I call it like so:

 log("My name is %s, and I like %s", "Dave", "Javascript");

I get this (it doesn't recognize "Javascript" as a 3rd argument):

 My name is Dave, and I like %s

If I call this:

 log("My name is %s, and I like %s", ["Dave", "Javascript"]);

then it treats the second arg as an array (it doesn't expand to multiple args). What trick am I missing to get it to expand the optional args?

Answer 1

You're looking for the arguments identifier, which is an array-like object (but not an actual array) containing all of the arguments that were passed to the function.

In your example, you can get an array containing all of the arguments after the first one like this:

var values = Array.prototype.slice.call(arguments, 1);

Answer 2

EDIT: I was surprised this didn't work so I went back, looking at all the above.

Dave, If you want to call it like this:

log("My name is %s, and I like %s", 'Dave', 'Javascript');

Then the simplest solution is this:

function log() {
    if(console.log !== null){
        console.log.apply(console,arguments);
    }
}

Oh, and console.log == true didn't work in either FF or Chrome for me. Only console.log != null worked. And nothing worked in IE7, go figure.

ORIGINAL(bad) answer:

Javascript has a special 'arguments' variable that does exactly what you want.

   function log(msg, arguments) {
       if(config.log == true){
         console.log(msg, arguments);
       }
   }

Answer 3

if(!window.log && console && console.log) window.log = console.log;

Answer 4

Though this isn't jQuery related, I can try answer it anyway :)

Following might work (untested):

function log(msg, values) {
  if(typeof config.log != 'undefined' ) {
    if( typeof values != 'Array' ) {
      values = [values];
    }
    values.unshift( msg );
    console.log.apply( this, values );
  }
}

Answer 5

@azatoth created an intelligent answer, but since won't work in Chrome I would use simple string concatenation instead:

function log(msg, values) {

    if (undefined != console) {
        var newArg = '';
        var newMsg = msg.split('%s');

        if (undefined != values) {
            for (i=0; i < (newMsg.length-1); i++) {
                newArg += newMsg[i] + values[i];
            }
        } else {
            newArg = newMsg[0];
        }

        console.log( newArg );
    }

}