Pascal's Triangle Example

triangle.js

pascalTriangle(10);

function pascalTriangle(levels) {
  return _.reduce(_.range(levels), function(triangle, i) {
    var row = _.reduce(_.range(i + 1), function(row, j) {
      var isFirst = j === 0;
      var isLast = j === i;
      if (isFirst || isLast) {
        row.push(1);
      } else {
        var sum = triangle[i - 1][j - 1] + triangle[i - 1][j];
        row.push(sum);
      }
      return row;
    }, [])
    triangle.push(row);
    return triangle;
  }, [])
}