HackerRank solutions - Simple Array Sum

Doing this so that I can document solutions for HackerRank for myself and discuss runtime complexities with other and try to come up with better solutions.

HackerRank - Simple Array Sum

// solution
function simpleArraySum(n, ar) {
    // Complete this function
    return ar.reduce( function( acc, val ) {
        return acc + val;
    } );
}

I think using the native js reduce function is simple solution without using for loops.