lbry-desktop/ui/util/deep-equal.js

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2019-09-26 18:07:11 +02:00
/* eslint-disable */
// underscore's deep equal function
// https://github.com/jashkenas/underscore/blob/master/underscore.js#L1189
export default function isEqual(a, b, aStack, bStack) {
// Identical objects are equal. `0 === -0`, but they aren't identical.
// See the [Harmony `egal` proposal](http://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);
}
function deepEq(a, b, aStack, bStack) {
// Compare `[[Class]]` names.
var className = toString.call(a);
if (className !== toString.call(b)) return false;
switch (className) {
// Strings, numbers, regular expressions, dates, and booleans 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 SymbolProto.valueOf.call(a) === SymbolProto.valueOf.call(b);
}
var areArrays = className === '[object Array]';
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 &&
!(
typeof aCtor === 'function' &&
aCtor instanceof aCtor &&
typeof bCtor === 'function' &&
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 (!isEqual(a[length], b[length], aStack, bStack)) return false;
}
} else {
// Deep compare objects.
var keys = Object.keys(a),
key;
length = keys.length;
// Ensure that both objects contain the same number of properties before comparing deep equality.
if (Object.keys(b).length !== length) return false;
while (length--) {
// Deep compare each member
key = keys[length];
if (!(has(b, key) && isEqual(a[key], b[key], aStack, bStack))) return false;
}
}
// Remove the first object from the stack of traversed objects.
aStack.pop();
bStack.pop();
return true;
}
function has(obj, path) {
return obj != null && hasOwnProperty.call(obj, path);
}
/* eslint-enable */