实现一个array_diff函数，找出2个或多个数组中唯一存在的数字，组成新的数组。

//找出多个数组中唯一存在的数字，组成新的数组function array_diff() {    var hash = {},        arr = [],        midArray = [],        result = [];    for (i in arguments) {        arr = arr.concat(arguments[i]);    }    for (i in arr) {        if (isNaN(hash[arr[i]]) && arr[i] <= "9" && arr[i] >= "0") {            midArray.push(arr[i]);            hash[arr[i]] = midArray.length - 1;        } else if (arr[i] <= "9" && arr[i] >= "0") {            delete midArray[hash[arr[i]]];        }    }    for (i in midArray) {        result.push(midArray[i]);    }    return result;}//测试array_diff函数var a = [1, 2, 3, "a"];var b = [2, 3, 4, "b"];var c = [3, 4, 5, "d"];alert("["+array_diff(a, b, c)+"]") //输出[1,5]