Calculate the sum of positive numbers in an Array

Given an array of numbers, return the summation of all positive numbers in the array.

Sample Code:

function sumPos(arr) {
// Enter your logic here...
}

Examples:

Input: [1,2,3,-999]
Output: 6
Explanation: The positive numbers are 1,2,3.

Input: [1,-2,-3,-999]
Output: 1
Explanation: The only positive number is 1.