This function acts like PHPs native print_r or var_dump and will dump out ANY variable to the console. Originally written for Appcelerator Titanium (using Ti.API.info instead of console.log) but tweaked to work with the console. There are plenty of alternatives to this, however I wanted to write my own so I could control the format / have a go :-)

dump.js

/**
 * DUMP
 *
 *	Dumps a variable in a readable form to the console, this is a recursive function
 *	so be careful of nested references that may cause it to overflow... (untested for that)
 *
 *	@v		ANYTHING		[Any variable]
 *	@name		STRING			[The name of the variable, optional, used internally when looping objects and arrays]
 *	@spacing	STRING			[The prefix spacing, used internally when looping objects and arrays]
 */
 var dump = function(v, name, spacing){
	var n;
	// Default the spacing to none (incremented on subsequent calls)
	spacing = spacing || '';
	// If we've been given a name, append a ": "
	name = name ? name + ': ' : '';
	// Figure out the type, fixes for NULL and ARRAY
	var type = typeof v;
	if(type == 'object'){
		if(v === null){
			type = 'null';
		} else if(Object.prototype.toString.call(v) === '[object Array]'){
			type = 'array';
		}
	}
	// Switch the type
	switch(type){
		case 'number':
			console.log(spacing + name + '[Num] ' + v);
			break;
		case 'string':
			console.log(spacing + name + '[Str] ' + v);
			break;
		case 'boolean':
			console.log(spacing + name + '[Boo] ' + v);
			break;
		case 'null':
			console.log(spacing + name + '[Nul] ' + v);
			break;
		case 'undefined':
			console.log(spacing + name + '[Und] ' + v);
			break;
		case 'object':
			console.log(spacing + name + '[Obj] {');
			for(n in v){
				dump(v[n], n, (spacing+'  '));
			}
			console.log(spacing + '}');
			break;
		case 'array':
			console.log(spacing + name + '[Arr] (');
			for(n in v){
				dump(v[n], n, (spacing+'  '));
			}
			console.log(spacing + ')');
			break;
	}
};

example

dump('string');
[Str] string

dump(123);
[Num] 123

dump([ 1, 2, 'a', 'b', null, true, false ]);
[Arr] (
  0: [Num] 1
  1: [Num] 2
  2: [Str] a
  3: [Str] b
  4: [Nul] null
  5: [Boo] true
  6: [Boo] false
)

dump({ 'a': 1, 'b': 2, 'c': null, false: true, 'ar': [ 1, 2, 3, null ] });
[Obj] {
  a: [Num] 1
  b: [Num] 2
  c: [Nul] null
  false: [Boo] true
  ar: [Arr] (
    0: [Num] 1
    1: [Num] 2
    2: [Num] 3
    3: [Nul] null
  )
}

dump(null);
[Nul] null

dump();
[Und] undefined