Pascal Triangle - Challenge

pascalTriangle.js

/**
Instructions
Compute Pascal's triangle up to a given number of rows.

In Pascal's Triangle each number is computed by adding the numbers to the right and left of the current position in the previous row.

    1
   1 1
  1 2 1
 1 3 3 1
1 4 6 4 1
# ... etc

*/

export const rows = (rows) => {
  // if row = 1 then 1
  // row =2 => 0+1 and 0+1
  // row = 3 => 
  let triangle = new Array(rows);

  if (rows === 0) return [];
  
  triangle = [[1]] // base case

  for (let i = 1; i < rows; i++) {
    triangle[i] = new Array(i+1)
    for (let j = 0; j < i+1; j++) {
      const prevRowValue = computeTriangle(triangle[i-1], j, i)
      triangle[i][j] = prevRowValue
    }  
  }
  return triangle
};

const computeTriangle = (prevRow, rowIndex, maxVal) => {
  if (rowIndex == 0 || rowIndex >= maxVal) {
    return prevRow[0] // 0th index will give us 1 always
  }
  else {
    return prevRow[rowIndex-1] + prevRow[rowIndex]
  }
}