meteor/packages/check/isPlainObject.js

// Copy of jQuery.isPlainObject for the server side from jQuery v1.11.2.

var class2type = {};

var toString = class2type.toString;

var hasOwn = class2type.hasOwnProperty;

var support = {};

// Populate the class2type map
_.each("Boolean Number String Function Array Date RegExp Object Error".split(" "), function(name, i) {
  class2type[ "[object " + name + "]" ] = name.toLowerCase();
});

function type( obj ) {
  if ( obj == null ) {
    return obj + "";
  }
  return typeof obj === "object" || typeof obj === "function" ?
    class2type[ toString.call(obj) ] || "object" :
    typeof obj;
}

function isWindow( obj ) {
  /* jshint eqeqeq: false */
  return obj != null && obj == obj.window;
}

exports.isPlainObject = function( obj ) {
  var key;

  // Must be an Object.
  // Because of IE, we also have to check the presence of the constructor property.
  // Make sure that DOM nodes and window objects don't pass through, as well
  if ( !obj || type(obj) !== "object" || obj.nodeType || isWindow( obj ) ) {
    return false;
  }

  try {
    // Not own constructor property must be Object
    if ( obj.constructor &&
         !hasOwn.call(obj, "constructor") &&
         !hasOwn.call(obj.constructor.prototype, "isPrototypeOf") ) {
      return false;
    }
  } catch ( e ) {
    // IE8,9 Will throw exceptions on certain host objects #9897
    return false;
  }

  // Support: IE<9
  // Handle iteration over inherited properties before own properties.
  if ( support.ownLast ) {
    for ( key in obj ) {
      return hasOwn.call( obj, key );
    }
  }

  // Own properties are enumerated firstly, so to speed up,
  // if last one is own, then all properties are own.
  for ( key in obj ) {}

  return key === undefined || hasOwn.call( obj, key );
};