util: simplify isPrimitve

[vkurchatkin]

Everything that is not an object should be a primitive.

R=@trevnorris

[seishun]

How about something simpler still:

return Object(arg) !== arg;

[micnic]

Or

return arg === null || typeof arg !== 'object';

[seishun]

@micnic that would return true for functions.

[micnic]

@seishun, oops, I read in the commit description Everything that is not an object should be a primitive..

[vkurchatkin]

@seishun looks neat, but probably involves unnecessary allocation

[vkurchatkin]

@seishun Here is how it's implemented in v8:

function ToObject(x) {
  if (IS_STRING(x)) return new $String(x);
  if (IS_NUMBER(x)) return new $Number(x);
  if (IS_BOOLEAN(x)) return new $Boolean(x);
  if (IS_SYMBOL(x)) return %NewSymbolWrapper(x);
  if (IS_NULL_OR_UNDEFINED(x) && !IS_UNDETECTABLE(x)) {
    throw %MakeTypeError('undefined_or_null_to_object', []);
  }
  return x;
}

[zloirock]

@seishun http://jsperf.com/core-js-isobject

[trevnorris]

I can't find any failures for edge cases. LGTM

[bnoordhuis]

I think it fits on one line now?

[bnoordhuis]

LGTM but there's a typo in the commit log: s/isPrimitve/isPrimitive/

[vkurchatkin]

Fixed everything and landed b9d3928