peaks.js

(function(window){

  function sum_peaked_array(peaked_array){
    var lowest_array_peak, sum = 0;
    lowest_array_peak = Math.min(peaked_array[0],peaked_array[peaked_array.length-1]);

    for(var i=1; i<peaked_array.length-1; i+=1){
      sum += lowest_array_peak - peaked_array[i];
    }
    return sum;
  }

  window.sum_array_valleys = function(input_array){
    var total = 0, right_peak_index = 1;

    for(var i=1; i<input_array.length; i+=1){
      if(input_array[i] >= input_array[0]){
        right_peak_index = i;
        break;
      }
      else if(input_array[i] > input_array[right_peak_index]){
        right_peak_index = i;
      }
    }

    total = right_peak_index > 1 ? sum_peaked_array(input_array.slice(0, right_peak_index+1)) : 0;

    if(right_peak_index < input_array.length){
      return total + sum_array_valleys(input_array.splice(right_peak_index))
    }
    else{
      return total;
    }
  }

})(window);