Relative Ranks

Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who will be awarded medals: “Gold Medal”, “Silver Medal” and “Bronze Medal”.

var findRelativeRanks = function(nums) {
    var res = [];
    var tmp = [];
    var obj = {};
    tmp = nums.slice();
    tmp.sort(function(a,b) {return b - a})
    obj[tmp[]]  = 'Gold Medal';
    obj[tmp[]] = 'Silver Medal';
    obj[tmp[]] = 'Bronze Medal';
    for(var m = ; m < tmp.length; m++) {
        obj[tmp[m]] = m +  + ''
    }

    for(var j = ; j < nums.length; j++) {
        res.push(obj[nums[j]])
    }

    return res
};