package.cjs.isEqual.js Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of underscore Show documentation
JavaScript's functional programming helper library.
The newest version!
var underscore = require('./underscore.js');
var _setup = require('./_setup.js');
var _getByteLength = require('./_getByteLength.js');
var isTypedArray = require('./isTypedArray.js');
var isFunction = require('./isFunction.js');
var _stringTagBug = require('./_stringTagBug.js');
var isDataView = require('./isDataView.js');
var keys = require('./keys.js');
var _has = require('./_has.js');
var _toBufferView = require('./_toBufferView.js');

// We use this string twice, so give it a name for minification.
var tagDataView = '[object DataView]';

// Internal recursive comparison function for `_.isEqual`.
function eq(a, b, aStack, bStack) {
  // Identical objects are equal. `0 === -0`, but they aren't identical.
  // See the [Harmony `egal` proposal](https://wiki.ecmascript.org/doku.php?id=harmony:egal).
  if (a === b) return a !== 0 || 1 / a === 1 / b;
  // `null` or `undefined` only equal to itself (strict comparison).
  if (a == null || b == null) return false;
  // `NaN`s are equivalent, but non-reflexive.
  if (a !== a) return b !== b;
  // Exhaust primitive checks
  var type = typeof a;
  if (type !== 'function' && type !== 'object' && typeof b != 'object') return false;
  return deepEq(a, b, aStack, bStack);
}

// Internal recursive comparison function for `_.isEqual`.
function deepEq(a, b, aStack, bStack) {
  // Unwrap any wrapped objects.
  if (a instanceof underscore) a = a._wrapped;
  if (b instanceof underscore) b = b._wrapped;
  // Compare `[[Class]]` names.
  var className = _setup.toString.call(a);
  if (className !== _setup.toString.call(b)) return false;
  // Work around a bug in IE 10 - Edge 13.
  if (_stringTagBug.hasDataViewBug && className == '[object Object]' && isDataView(a)) {
    if (!isDataView(b)) return false;
    className = tagDataView;
  }
  switch (className) {
    // These types are compared by value.
    case '[object RegExp]':
      // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
    case '[object String]':
      // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
      // equivalent to `new String("5")`.
      return '' + a === '' + b;
    case '[object Number]':
      // `NaN`s are equivalent, but non-reflexive.
      // Object(NaN) is equivalent to NaN.
      if (+a !== +a) return +b !== +b;
      // An `egal` comparison is performed for other numeric values.
      return +a === 0 ? 1 / +a === 1 / b : +a === +b;
    case '[object Date]':
    case '[object Boolean]':
      // Coerce dates and booleans to numeric primitive values. Dates are compared by their
      // millisecond representations. Note that invalid dates with millisecond representations
      // of `NaN` are not equivalent.
      return +a === +b;
    case '[object Symbol]':
      return _setup.SymbolProto.valueOf.call(a) === _setup.SymbolProto.valueOf.call(b);
    case '[object ArrayBuffer]':
    case tagDataView:
      // Coerce to typed array so we can fall through.
      return deepEq(_toBufferView(a), _toBufferView(b), aStack, bStack);
  }

  var areArrays = className === '[object Array]';
  if (!areArrays && isTypedArray(a)) {
      var byteLength = _getByteLength(a);
      if (byteLength !== _getByteLength(b)) return false;
      if (a.buffer === b.buffer && a.byteOffset === b.byteOffset) return true;
      areArrays = true;
  }
  if (!areArrays) {
    if (typeof a != 'object' || typeof b != 'object') return false;

    // Objects with different constructors are not equivalent, but `Object`s or `Array`s
    // from different frames are.
    var aCtor = a.constructor, bCtor = b.constructor;
    if (aCtor !== bCtor && !(isFunction(aCtor) && aCtor instanceof aCtor &&
                             isFunction(bCtor) && bCtor instanceof bCtor)
                        && ('constructor' in a && 'constructor' in b)) {
      return false;
    }
  }
  // Assume equality for cyclic structures. The algorithm for detecting cyclic
  // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.

  // Initializing stack of traversed objects.
  // It's done here since we only need them for objects and arrays comparison.
  aStack = aStack || [];
  bStack = bStack || [];
  var length = aStack.length;
  while (length--) {
    // Linear search. Performance is inversely proportional to the number of
    // unique nested structures.
    if (aStack[length] === a) return bStack[length] === b;
  }

  // Add the first object to the stack of traversed objects.
  aStack.push(a);
  bStack.push(b);

  // Recursively compare objects and arrays.
  if (areArrays) {
    // Compare array lengths to determine if a deep comparison is necessary.
    length = a.length;
    if (length !== b.length) return false;
    // Deep compare the contents, ignoring non-numeric properties.
    while (length--) {
      if (!eq(a[length], b[length], aStack, bStack)) return false;
    }
  } else {
    // Deep compare objects.
    var _keys = keys(a), key;
    length = _keys.length;
    // Ensure that both objects contain the same number of properties before comparing deep equality.
    if (keys(b).length !== length) return false;
    while (length--) {
      // Deep compare each member
      key = _keys[length];
      if (!(_has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
    }
  }
  // Remove the first object from the stack of traversed objects.
  aStack.pop();
  bStack.pop();
  return true;
}

// Perform a deep comparison to check if two objects are equal.
function isEqual(a, b) {
  return eq(a, b);
}

module.exports = isEqual;