018.js

// By starting at the top of the triangle below and moving to adjacent numbers 
// on the row below, the maximum total from top to bottom is 23.

//       3
//      7 4
//     2 4 6
//    8 5 9 3

// That is, 3 + 7 + 4 + 9 = 23.

// Find the maximum total from top to bottom of the triangle below:

var TRIANGLE = [
    ['75'],
    ['95','64'],
    ['17','47','82'],
    ['18','35','87','10'],
    ['20','04','82','47','65'],
    ['19','01','23','75','03','34'],
    ['88','02','77','73','07','63','67'],
    ['99','65','04','28','06','16','70','92'],
    ['41','41','26','56','83','40','80','70','33'],
    ['41','48','72','33','47','32','37','16','94','29'],
    ['53','71','44','65','25','43','91','52','97','51','14'],
    ['70','11','33','28','77','73','17','78','39','68','17','57'],
    ['91','71','52','38','17','14','91','43','58','50','27','29','48'],
    ['63','66','04','68','89','53','67','30','73','16','69','87','40','31'],
    ['04','62','98','27','23','09','70','98','73','93','38','53','60','04','23']
];

function maxRoute(triangle) {
    var intg = function(x) {
        return parseInt(x, 10);
    };
    var len = triangle.length - 1;
    while (len--) {
        for (var i = 0; i <= len; i++) {
            triangle[len][i] = Math.max(
                intg(triangle[len][i]) + intg(triangle[len+1][i]),
                intg(triangle[len][i]) + intg(triangle[len+1][i+1])
            );
        }
    }
    return triangle[0][0];
}

console.log( maxRoute(TRIANGLE) );