对象是否相等

//如果用JSON.stringify转化属性顺序不同，也不相等；
//而且不支持无法对函数 、RegExp等特殊对象的克隆

function deepCompare(x, y) {
    var i, l, leftChain, rightChain;

    function compare2Objects(x, y) {
        var p;

        // remember that NaN === NaN returns false
        // and isNaN(undefined) returns true
        if (isNaN(x) && isNaN(y) && typeof x === 'number' && typeof y === 'number') {
            return true;
        }

        // Compare primitives and functions.     
        // Check if both arguments link to the same object.
        // Especially useful on the step where we compare prototypes
        if (x === y) {
            return true;
        }

        // Works in case when functions are created in constructor.
        // Comparing dates is a common scenario. Another built-ins?
        // We can even handle functions passed across iframes
        if ((typeof x === 'function' && typeof y === 'function') || (x instanceof Date && y instanceof Date) || (x instanceof RegExp && y instanceof RegExp) || (x instanceof String && y instanceof String) || (x instanceof Number && y instanceof Number)) {
            return x.toString() === y.toString();
        }

        // At last checking prototypes as good as we can
        if (!(x instanceof Object && y instanceof Object)) {
            return false;
        }

        if (x.isPrototypeOf(y) || y.isPrototypeOf(x)) {
            return false;
        }

        if (x.constructor !== y.constructor) {
            return false;
        }

        if (x.prototype !== y.prototype) {
            return false;
        }

        // Check for infinitive linking loops
        if (leftChain.indexOf(x) > -1 || rightChain.indexOf(y) > -1) {
            return false;
        }

        // Quick checking of one object being a subset of another.
        // todo: cache the structure of arguments[0] for performance
        for (p in y) {
            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
                return false;
            } else if (typeof y[p] !== typeof x[p]) {
                return false;
            }
        }

        for (p in x) {
            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
                return false;
            } else if (typeof y[p] !== typeof x[p]) {
                return false;
            }

            switch (typeof(x[p])) {
            case 'object':
            case 'function':

                leftChain.push(x);
                rightChain.push(y);

                if (!compare2Objects(x[p], y[p])) {
                    return false;
                }

                leftChain.pop();
                rightChain.pop();
                break;

            default:
                if (x[p] !== y[p]) {
                    return false;
                }
                break;
            }
        }

        return true;
    }

    if (arguments.length < 1) {
        return true;
    }

    for (i = 1, l = arguments.length; i < l; i++) {

        leftChain = []; //Todo: this can be cached
        rightChain = [];

        if (!compare2Objects(arguments[0], arguments[i])) {
            return false;
        }
    }

    return true;
}

const obj1 = {
    name: '张三',
    age: 23,
    obj: {
        name: '李四',
        age: 46
    },
    arr: [1, 2, 3],
    date: new Date(23),
    reg: new RegExp('abc'),
    fun: () = > {}
}
const obj2 = {
    name: '张三',
    age: 23,
    obj: {
        name: '李四',
        age: 46
    },
    arr: [1, 2, 3],
    date: new Date(23),
    reg: new RegExp('abc'),
    fun: () = > {}
}
console.log(deepCompare(obj1, obj2)) // true