Third Maximum Number.js

/*Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).

Example 1:
Input: [3, 2, 1]

Output: 1

Explanation: The third maximum is 1.
Example 2:
Input: [1, 2]

Output: 2

Explanation: The third maximum does not exist, so the maximum (2) is returned instead.
Example 3:
Input: [2, 2, 3, 1]

Output: 1

Explanation: Note that the third maximum here means the third maximum distinct number.
Both numbers with value 2 are both considered as second maximum.*/

/**
 * @param {number[]} nums
 * @return {number}
 */
var thirdMax = function(nums) {
    max = Number.NEGATIVE_INFINITY
    smax = Number.NEGATIVE_INFINITY
    tmax = Number.NEGATIVE_INFINITY
    for(i=0; i<nums.length; i++){
        if(nums[i] > max){
            tmax = smax
            smax = max
            max = nums[i]
        }
        if(nums[i] > smax && nums[i] < max){
            tmax = smax
            smax = nums[i]
        }
        if(nums[i] > tmax && nums[i] < smax){
            tmax = nums[i]
        }
    }
    
    if(tmax != Number.NEGATIVE_INFINITY)
        return tmax
    else
        return max
};