Google interview question

by kpulkit29

HTML

<table cellspacing=0>
  <tbody class='done'>
    
  </tbody>
</table>

JavaScript

let r=4, c=5;
let arr = [];
let tBody = document.querySelector('.done');
const row = document.createElement('tr');
for(let i=0;i<c;i++) { 
arr[0] = arr[0] || [];
const col = document.createElement('td');
  if(i&1) {
  		arr[0][i] = r*(i+1)
  } else{ 
  		arr[0][i] = (r*i)+1;
  }
  col.append(arr[0][i]);
  row.appendChild(col);
  tBody.appendChild(row);
}
for(let i=1;i<r;i++) {
	arr[i] = arr[i] || [];
  const row = document.createElement('tr');
	for(let j=0;j<c;j++) {
  const col = document.createElement('td');
  if(j&1) {
  		arr[i][j] = arr[i-1][j]-1;
  } else{ 
  		arr[i][j] = arr[i-1][j]+1;
  }
  col.append(arr[i][j]);
  row.appendChild(col);
  }
  tBody.appendChild(row);
}
console.log(arr);