how can i read data from column a in excel?

You cannot just pass the string and expect that you’ll get that column, you have to find the name of the cells which you will accrue.

const columnName = Object.keys(worksheet).find(key=> worksheet[key].v === address_of_cell);

Finding the name is done by passing the ‘Emails’ and searching which cell names are to be parsed.

This will work:

const xlsx = require('xlsx');


const emails = [];
var workbook = xlsx.readFile(`./view/assets/uploads/${filename}`);
var first_sheet_name = workbook.SheetNames[0];
var address_of_cell = 'Emails';
var worksheet = workbook.Sheets[first_sheet_name];
const columnName = Object.keys(worksheet).find(key=> worksheet[key].v === address_of_cell);

for (let key in worksheet) {
  if (key.toString()[0] === columnName[0]) {
    emails.push(worksheet[key].v);
  }
}
console.log('Result list', emails)

Likewise, instead of the for in loop you could stay functional and avoid array declaration and worksheet object reference

const emails = Object.entries(worksheet)
  .filter(([key, value]) => key.toString()[0] === columnName[0])
  .map(([key, value]) => value.v)