var pSlice = Array.prototype.slice; var Object_keys = typeof Object.keys === 'function'

? Object.keys
: function (obj) {
    var keys = [];
    for (var key in obj) keys.push(key);
    return keys;
}

;

var deepEqual = module.exports = function (actual, expected) {

// enforce Object.is +0 !== -0
if (actual === 0 && expected === 0) {
  return areZerosEqual(actual, expected);

// 7.1. All identical values are equivalent, as determined by ===.
} else if (actual === expected) {
  return true;

} else if (actual instanceof Date && expected instanceof Date) {
  return actual.getTime() === expected.getTime();

} else if (isNumberNaN(actual)) {
  return isNumberNaN(expected);

// 7.3. Other pairs that do not both pass typeof value == 'object',
// equivalence is determined by ==.
} else if (typeof actual != 'object' && typeof expected != 'object') {
  return actual == expected;

// 7.4. For all other Object pairs, including Array objects, equivalence is
// determined by having the same number of owned properties (as verified
// with Object.prototype.hasOwnProperty.call), the same set of keys
// (although not necessarily the same order), equivalent values for every
// corresponding key, and an identical 'prototype' property. Note: this
// accounts for both named and indexed properties on Arrays.
} else {
  return objEquiv(actual, expected);
}

};

function isUndefinedOrNull(value) {

return value === null || value === undefined;

}

function isArguments(object) {

return Object.prototype.toString.call(object) == '[object Arguments]';

}

function isNumberNaN(value) {

// NaN === NaN -> false
return typeof value == 'number' && value !== value;

}

function areZerosEqual(zeroA, zeroB) {

// (1 / +0|0) -> Infinity, but (1 / -0) -> -Infinity and (Infinity !== -Infinity)
return (1 / zeroA) === (1 / zeroB);

}

function objEquiv(a, b) {

if (isUndefinedOrNull(a) || isUndefinedOrNull(b))
  return false;

// an identical 'prototype' property.
if (a.prototype !== b.prototype) return false;
//~~~I've managed to break Object.keys through screwy arguments passing.
//   Converting to array solves the problem.
if (isArguments(a)) {
  if (!isArguments(b)) {
    return false;
  }
  a = pSlice.call(a);
  b = pSlice.call(b);
  return deepEqual(a, b);
}
try {
  var ka = Object_keys(a),
      kb = Object_keys(b),
      key, i;
} catch (e) {//happens when one is a string literal and the other isn't
  return false;
}
// having the same number of owned properties (keys incorporates
// hasOwnProperty)
if (ka.length != kb.length)
  return false;
//the same set of keys (although not necessarily the same order),
ka.sort();
kb.sort();
//~~~cheap key test
for (i = ka.length - 1; i >= 0; i--) {
  if (ka[i] != kb[i])
    return false;
}
//equivalent values for every corresponding key, and
//~~~possibly expensive deep test
for (i = ka.length - 1; i >= 0; i--) {
  key = ka[i];
  if (!deepEqual(a[key], b[key])) return false;
}
return true;

}