My solution to [Problem 11 project euler](http://projecteuler.net/problem=11). I took way too long to solve it using functional approach, also traversing diagonal grids and pick the tokens drove me nuts.

LargestProductGrid.js

var _und = require("./underscore-min.js"); //load underscore.js library in the current directory
var group = 4;

//parse it, because I'm too lazy to create the array by hand
var strGrid = "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";

strGrid = strGrid.split(" ");

var numGrid = [];
for (var x = 0; x < 20; x++){
	numGrid.push([]);
	for (var y = 0; y < 20; y++){
		numGrid[x].push( parseInt( strGrid.shift(), 10 ) );
	}

}

function product(base, number){
	return base * number;
}

function xy(isHorizontal, grid){
	var token = [];
	var temp = [];

	for (var x = 0; x < 20; x++){

		//store the temp array first before creating the token
		if (isHorizontal) {
			temp = grid[x];
		} else {
			for (var y = 0; y < 20; y++) {
				temp.push(grid[y][x]);
			}
		}

		//create the token. Use slice();
		for (var t = 0; t < temp.length; t++){
			token.push(temp.slice(t, t+group));
		}

		temp = [];
	}


	return token;
};

//hiks, we can't use slice() :(
//this is painful to create
function diag(isRight, grid){
	var token = [];
	var sign = (isRight) ? 1 : -1;
	var valX, valY;

	for (var x = 0; x < grid.length; x++){
		for (var y = 0; y < grid[x].length; y++){
			token[token.length] = [];
			for (var xDown = 0; xDown < group; xDown++) { 
				valX = x + xDown;
				valY = y - (sign * xDown);
				if ( valX >= grid.length) {continue;}
				if (  valY >= grid.length || valY < 0 ){continue;}
				
				token[token.length-1].push( grid[valX][valY] );
			}			
		}
	}

	return token;
};

var greatestVer = _und.max(
	_und.map( 
		xy(false, numGrid),
		function(element){
			return _und.reduce (
				element, product, 1
			);		
		}
	)
);


var greatestHor = _und.max(
	_und.map( 
		xy(true, numGrid),
		function(element){
			return _und.reduce (
				element, product, 1
			);		
		}
	)
);

var greatestDiagLeft = _und.max(
	_und.map( 
		diag(false, numGrid),
		function(element){
			return _und.reduce (
				element, product, 1
			);		
		}
	)
);

var greatestDiagRight = _und.max(
	_und.map( 
		diag(true, numGrid),
		function(element){
			return _und.reduce (
				element, product, 1
			);		
		}
	)
);

console.log(_und.max([greatestVer, greatestHor, greatestDiagLeft, greatestDiagRight]));