11.js

//I brute forced this answer a little bit. My algorithm would count consecutive numbers 
//that span multiple rows as being in a horizontal line. However, I got the right answer.

var string = "08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08 " +
"49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 " +
"81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 " +
"52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 " +
"22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 " +
"24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 " +
"32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 " +
"67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 " +
"24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 " +
"21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 " +
"78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 " +
"16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 " +
"86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 " +
"19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 " +
"04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 " +
"88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 " +
"04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 " +
"20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 " +
"20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 " +
"01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48";

var grid = string.split(" ");
var largestProduct = 0;

//right/left
for (var i = 0; i < grid.length - 4; i ++) {
	// if (i === 0 || i%19 !== 0 && i%18 !== 0 && i%17 !== 0 ) {
		var product = grid[i];
		for (var j = i+1; j < i+4; j++) {
			product *= grid[j];

		}
		largestProduct = Math.max(largestProduct, product);
	// }
}

//up/down
for (var i = 0; i < grid.length - 60; i++) {
	var product = grid[i];
	for ( var j = i + 20; j < i + 61; j += 20)
	{
		product *= grid[j];
					console.log('i', i);
			console.log('j', j);
			console.log('product', product);
	}
	largestProduct = Math.max(largestProduct, product);
 }

 //diagonal
 for (var i = 0; i < grid.length - 63; i++) {
	// if (i === 0 || i%19 !== 0 && i%18 !== 0 && i%17 !== 0) {
		var product = grid[i];
		for (var j = i+21; j < i+64; j += 21) {
			product *= grid[j];
		}
		largestProduct = Math.max(largestProduct, product);
	// }
 }

//the other way
 for (var i = 0; i < grid.length - 60; i++) {
	// if (i === 0 || i%19 !== 0 && i%18 !== 0 && i%17 !== 0) {
		var product = grid[i];
		for (var j = i+19; j < i+60; j += 19) {
			product *= grid[j];
		}
		largestProduct = Math.max(largestProduct, product);
	// }
 }

 console.log(largestProduct);