sum_of_a_sequence.js

/*
Your task is to make function, which returns the sum of a sequence of integers.

The sequence is defined by 3 non-negative values: begin, end, step.

If begin value is greater than the end, function should returns 0

Examples

sequenceSum(2,2,2) === 2
sequenceSum(2,6,2) === 12 // 2 + 4 + 6
sequenceSum(1,5,1) === 15 // 1 + 2 + 3 + 4 + 5
sequenceSum(1,5,3) === 5 // 1 + 4
*/
function sequenceSum(begin, end, step) {
  var sum=[];
   while(begin<=end) {
    sum.push(begin);
    begin=begin + step;
    }
return sum.reduce(function (a,b) {return a+b}, 0);
};