If the function is returning a Promise, and you want to do them serially (one at a time) instead of in parallel (start all at the same time), you'll need to wait for each before you start the next using then().
Also, note that your TEAM is just an export of an array (at least as presented), so you can't give it args, which is where the other error comes from.
When you have a list of things to do, the best way to do them is to have a queue which you run until you run out of files. In this case, it looks like your TEAM array is your queue, but since this is an export, I'd recommend not necessarily changing this, but instead copy it to another array which you can alter:
const args = process.argv.slice(2);
const TEAM = require('./teams');
const Excel = require('exceljs');
const workbook = new Excel.Workbook();
const writeNextFile = (queue) => {
// If we have nothing left in the queue, we're done.
if (!queue.length) {
return Promise.resolve();
}
const team = queue.shift(); // get the first element, take it out of the array
console.log("Starting Excel File generation for " + team.team_name);
var fhcw = require('../data_files/home/fhcw/' + team.friendly_name + '_home' + '.json');
fhcw = fhcw.map(Number);
// return this promise chain
return workbook.xlsx.readFile('./excel_files/blank.xlsx')
.then(function() {
var worksheet = workbook.getWorksheet(1);
// Write FHCW
for (i=0; i < fhcw.length; i++) {
col = i+6;
worksheet.getCell('E'+ col).value = fhcw[i];
}
console.log(team);
// not sure what you thought this would TEAM[args] would have translated to, but it wouldn't have been a string, so I put ??? for now
// also, making the assumption that writeFile() returns a Promise.
return workbook.xlsx.writeFile('./excel_files/' + team.??? + '/' + team.friendly_name + '.xlsx');
}).then(() => writeNextFile(queue));
}
writeNextFile(TEAM.slice(0)) // make a copy of TEAM so we can alter it
.then(() => console.log('Done'))
.catch(err => console.error('There was an error', err));
Basically, our function takes an array and will write the first team, then call itself recursively to call the next. Eventually it'll all resolve and you're end up with is a Promise that resolves at the end.
When it comes to Promises, you basically always need to chain them together. You won't be able to use a for loop for them, or any other standard loop for that matter.
If you wanted to write them all at once, it is a little cleaner, because you can just do a non-recursive map for each and use Promise.all to know when they are done.
const writeNextFile = (team) => {
console.log("Starting Excel File generation for " + team.team_name);
var fhcw = require('../data_files/home/fhcw/' + team.friendly_name + '_home' + '.json');
fhcw = fhcw.map(Number);
// return this promise chain
return workbook.xlsx.readFile('./excel_files/blank.xlsx')
.then(function() {
var worksheet = workbook.getWorksheet(1);
// Write FHCW
for (i=0; i < fhcw.length; i++) {
col = i+6;
worksheet.getCell('E'+ col).value = fhcw[i];
}
console.log(team);
// not sure what you thought this would TEAM[args] would have translated to, but it wouldn't have been a string, so I put ??? for now
// also, making the assumption that writeFile() returns a Promise.
return workbook.xlsx.writeFile('./excel_files/' + team.??? + '/' + team.friendly_name + '.xlsx');
});
}
Promise.all(TEAM.map(writeTeamFile))
.then(() => console.log('Done')
.catch(err => console.error('Error'));
Promises are for async, and generally when you have a group of things, you want to do them in parallel because it's faster. That's why the parallel version is a lot cleaner; we don't have to call things recursively.
