gistfile1.js

var userActivity = [
    1.2,
    2,
    0,
    74,
    6,
    3,
    0
];

var userActivity = [
    1.2,
    2,
    3,
    14,
    6,
    3,
    10
];


var weeklyScore = 0;

for (var i  = 0; i < 7; i++) {
    if (userActivity[i] == 0) {
        weeklyScore += 100;
    } else {
        weeklyScore += userActivity[i];
    }
}

console.log(weeklyScore);