You are given an integer array prices representing the daily price history of a stock, where prices[i] is the stock price on the ith day. A smooth descent period of a stock consists of one or more contiguous days such that the price on each day is l

getDescentPeriods.js

/**
 * @param {number[]} prices
 * @return {number}
 */
var getDescentPeriods = function(prices) {
    let total = 0;        // total number of descent periods
    let streak = 0;       // length of current descent streak

    for (let i = 0; i < prices.length; i++) {
        if (i > 0 && prices[i] === prices[i - 1] - 1) {
            // continue the descent streak
            streak += 1;
        } else {
            // reset streak (single day always counts)
            streak = 1;
        }
        total += streak;  // each day contributes 'streak' periods
    }

    return total;
};