find_max_profit.js

var stock_prices = [15,14,11,10,8,6,5,2,1];//[10,11,12,15,8,9,10,14,11];//[10, 9, 8, 10, 13, 11, 9, 10, 15];

var max_and_min = [];
var i = stock_prices.length - 1;
for (i; i >= 0; i--) {
    if (max_and_min.length && (max_and_min[0].min == null || max_and_min[0].min > stock_prices[i])) {
    	max_and_min[0].min = stock_prices[i];
    }
    
    if (!max_and_min.length || max_and_min[0].max < stock_prices[i]) {
        max_and_min.unshift({
            max: stock_prices[i],
            min: null
        });
    }
}

var most_profit_idx = -1;
var max_profit = null;
var temp_profit;
for (i=0; i < max_and_min.length; i++) {
    if (max_and_min[i].min === null) {
        continue;
    }
    temp_profit = max_and_min[i].max - max_and_min[i].min;
    if (max_profit === null || max_profit < temp_profit) {
        max_profit = temp_profit;
    }
}

console.log(max_and_min.length);
console.log(max_profit);