Underscore functions

function omit(obj, keys){
  
  if (typeof obj != 'object') {
    console.log("this is not an object");
    return obj;
  }
  
  var omitThisKey;
  if (keys instanceof Array) {
   omitThisKey = function(key) {
        if(keys.indexOf(key) > -1) {
          return true;
        }
    };
  }
  else if (typeof keys == 'function') {
    omitThisKey = keys.apply(key);
  }
  else if (typeof keys == 'object') {
   omitThisKey = function(key) {
       if (key == keys){
         return true;
       }
   } ;
  }
  
  for(var key in obj) {
    if(omitThisKey(key)) {
       delete obj[key] ;
    }   
  }
  
  return obj;
  
}