GetUniqueNumbers

JavaScript

var getFirstUniqueNumber = function(nums) {
    var number = null;
    var map = {};
    nums.forEach((val) => {
        if (!map[val] && (number === null)) number = val;
        if (map[val] && (number !== null)) number = null;
        map[val] = true;
    });
    return number;
};

var getLastUniqueNumber = function(nums) {
    var number = null;
    var map = {};
    nums.forEach((val) => {
        if (!map[val]) number = val;
        map[val] = true;
    });
    return number;
};


console.log(getFirstUniqueNumber([2, 2, 3, 3, 4]));
console.log(getLastUniqueNumber([2, 2, 3, 3, 4]));
console.log(getFirstUniqueNumber([7,2,1,1,3]));
console.log(getLastUniqueNumber([2,2,3,7]));