import _ from './underscore.js';
import { toString, SymbolProto } from './_setup.js';
import getByteLength from './_getByteLength.js';
import isTypedArray from './isTypedArray.js';
import isFunction from './isFunction.js';
import { hasDataViewBug } from './_stringTagBug.js';
import isDataView from './isDataView.js';
import keys from './keys.js';
import has from './_has.js';
import toBufferView from './_toBufferView.js';We use this string twice, so give it a name for minification.
var tagDataView = '[object DataView]';Perform a deep comparison to check if two objects are equal.
export default function isEqual(a, b) {Keep track of which pairs of values need to be compared. We will be trampolining on this stack instead of using function recursion. (CVE-2026-27601)
var todo = [{a: a, b: b}];Initializing stacks of traversed objects for cycle detection.
var aStack = [], bStack = [];Keep traversing pairs until there is nothing left to compare.
while (todo.length) {
var frame = todo.pop();As a special case, a single true on the todo means that we can
unwind the cycle detection stacks.
if (frame === true) {Remove the first object from the stack of traversed objects.
aStack.pop();
bStack.pop();
continue;
}
a = frame.a;
b = frame.b;Identical objects are equal. 0 === -0, but they aren’t identical.
See the Harmony egal proposal.
if (a === b) {
if (a !== 0 || 1 / a === 1 / b) continue;
return false;
}null or undefined only equal to itself (strict comparison).
if (a == null || b == null) return false;NaNs are equivalent, but non-reflexive.
if (a !== a) {
if (b !== b) continue;
return false;
}Exhaust primitive checks
var type = typeof a;
if (type !== 'function' && type !== 'object' && typeof b != 'object') return false;Unwrap any wrapped objects.
if (a instanceof _) a = a._wrapped;
if (b instanceof _) b = b._wrapped;Compare [[Class]] names.
var className = toString.call(a);
if (className !== toString.call(b)) return false;Work around a bug in IE 10 - Edge 13.
if (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").
if ('' + a === '' + b) continue;
return false;
case '[object Number]':
todo.push({a: +a, b: +b});
continue;
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.
if (+a === +b) continue;
return false;
case '[object Symbol]':
if (SymbolProto.valueOf.call(a) === SymbolProto.valueOf.call(b)) continue;
return false;
case '[object ArrayBuffer]':
case tagDataView:Coerce to typed array so we can fall through.
todo.push({a: toBufferView(a), b: toBufferView(b)});
continue;
}
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) continue;
areArrays = true;
}
if (!areArrays) {
if (typeof a != 'object' || typeof b != 'object') return false;Objects with different constructors are not equivalent, but Objects or Arrays
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.
var length = aStack.length;
while (length--) {Linear search. Performance is inversely proportional to the number of unique nested structures.
if (aStack[length] === a) {Cycle detected. Break out of the inner loop and continue the outer loop. Step 1:
if (bStack[length] === b) break;
return false;
}
}Step 2, use length to verify whether we detected a cycle:
if (length >= 0) continue;Add the first object to the stack of traversed objects.
aStack.push(a);
bStack.push(b);Remember to remove them again after the recursion below.
todo.push(true);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--) {
todo.push({a: a[length], b: b[length]});
}
} 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)) return false;
todo.push({a: a[key], b: b[key]});
}
}
}We made it to the end and found no differences.
return true;
}