JavaScript系列之值的深比较

比较两个值（对象或基本类型）是否相等

• 参考UnderScore的eq方法

 var Utils = {};
    Utils.keys = function(obj) {
        if(Array.isArray(obj)) return [];
        else if(Object.keys) return Object.keys(obj)
    };
    Utils.has = function(obj, key){
        return Object.prototype.hasOwnProperty.call(obj, key)
    }
    function equals(a, b, aStack, bStack) {
        var aStack = aStack? aStack : [];
        var bStack = bStack? bStack : [];
        //对原始类型数据进行比较,
        // 排除掉0和-0的相等性：
        if (a === b) {
            return a !== 0 || 1 / a === 1 / b;
        }
        //判断null和undefined，null==undefined->true
        if (a == null || b == null) {
            return a === b;
        }

        var className = Object.prototype.toString.call(a);
        if (className !== Object.prototype.toString.call(b)) {
            return false;
        }
        switch (className) {
            //统一转换为字符串后进行严格相等的判断：
            case '[object RegExp]':
            case '[object String]':
                return '' + a === '' + b;
            //应该把NaN看做相等，把0和-0看成不等
            case '[object Number]':
                if (+a !== +a) return +b !== +b;
                return +a === 0 ? 1 / +a === 1 / b : +a === +b;
            //直接判断
            case '[object Date]':
            case '[object Boolean]':
                return +a === +b;
        }

        //对数组和对象进行判断
        var areArrays = className === '[object Array]';
        if (!areArrays) {
            if (typeof a != 'object' || typeof b != 'object') return false;

            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;
            }
        }
        var length = aStack.length;
        while (length--) {
            if (aStack[length] === a) return bStack[length] === b;
        }

        aStack.push(a);
        bStack.push(b);
        var size, result;
        if (areArrays) {
            size = a.length;
            result = size === b.length;
            if (result) {
                while (size--) {
                    if (!(result = equals(a[size], b[size], aStack, bStack))) break;
                }
            }
        } else {
            var keys = Utils.keys(a), key;
            size = keys.length;
            result = Utils.keys(b).length === size;
            if (result) {
                while (size--) {
                    key = keys[size];
                    if (!(result = Utils.has(b, key) && equals(a[key], b[key], aStack, bStack))) break;
                }
            }
        }
        aStack.pop();
        bStack.pop();
        return result;
    }

示例：

var p1 = {name:"jack",age:18}; 
var p2 = {name:"lucy",age:10}; 
var p3 = {name:"jack",age:18}; 
console.log(equal(p1,p2));//false 
console.log(equal(p1,p3));//true 
console.log(equal(p1,{name:"jack",age:18}));//true