Read column wise values using XLSX - node.js

Question

How to read Column wise values from excel using nodejs(node-xlsx) ? Please advise.
I want to read Col A data, then Col B and so on, if any data exists in other columns, then put data in array.
I am able to read A1, B1, A2, B2... this way but not A1, A2, A3... then B1, B2, B3... etc.
Sample column wise data
I did custom way but not able to go to col C dynamically.
const xlsxfile = require("xlsx");
var arr = [];
const spreadsheet = xlsxfile.readFile('./Code.xlsx');
const sheets = spreadsheet.SheetNames;
console.log('Sheet Names -- ' + sheets);
const firstSheetName = sheets[0];
const firstSheet = spreadsheet.Sheets[firstSheetName];
console.log(firstSheet);
for (z in firstSheet) {
if (z[0] === '!') continue;
//parse out the column, row, and value
var tt = 0;
for (var i = 0; i < z.length; i++) {
if (!isNaN(z[i])) {
tt = i;
break;
}
};
var col = z.substring(0, tt);
var row = parseInt(z.substring(tt));
for (; ; row++) { // looping over all rows in a column
const firstCol = firstSheet[col+''+row];
if (!firstCol) {
break;
}
let value = firstCol.w;
//console.log(value);
if (value)
if (!arr.includes(value))
arr.push(value);
else
continue;
else
break;
}
}
console.log('final array = '+arr);

Answer 1

I somehow achieved my goal in very bad way. In top most loop it's always trying to get A1, B1, C1 like that. But in between I hijacked and looping all rows.
So in that way, I am keeping one track of what's my last column and comparing in next is same column or new column. if same column, I am existing.
But is there any better way to get all values may be in array format column wise?
const xlsxfile = require("xlsx");
var arr = [];
const spreadsheet = xlsxfile.readFile('./Code.xlsx');
const sheets = spreadsheet.SheetNames;
console.log('Sheet Names -- ' + sheets);
const firstSheetName = sheets[0];
const firstSheet = spreadsheet.Sheets[firstSheetName];
console.log(firstSheet);
let earliercol = []; // keeping a track
for (z in firstSheet) {
if (z[0] === '!') continue;
//parse out the column, row, and value
let tt = 0;
for (let i = 0; i < z.length; i++) {
if (!isNaN(z[i])) {
tt = i;
break;
}
};
let col = z.substring(0, tt);
let row = parseInt(z.substring(tt));
if (earliercol.includes(col)) // checking current col already traversed or not
break;
earliercol.push(col); // assigning current col name
//var value = worksheet[z].v;
for (; ; row++) {
//const firstCol = firstSheet['A' + i];
const firstCol = firstSheet[col+''+row];
if (!firstCol) {
break;
}
let value = firstCol.w;
//console.log(value);
if (value)
if (!arr.includes(value))
arr.push(value);
else
continue;
else
break;
}
}
console.log('final array = '+arr);