a JavaScript function to print out a table with right-justified columns

table.js

// Print out a simple table with right-justified columns of strings.
// This can handle some columns having fewer entries than others.
// (For mid-table missing entries, provide empty strings.)
// The `cols` value is an array of arrays of strings, the columns of the table.
// The optional `topSep` is a string the indicates the separator to use in the
// top row only. If you don't provide topSep, a single space is used.
function showTableWithColumns(cols, topSep) {
    
    if (topSep === undefined) topSep = ' ';

    let numRows = Math.max(...cols.map(x => x.length));
    cols.forEach(col => {
        while (col.length < numRows) col.push('');
    });

    // Find the maximum width in each column.
    let widths = cols.map(col => Math.max(...col.map(x => x.length)));

    let nonTopSep = ''.padStart(topSep.length);
    for (let i = 0; i < numRows; i++) {
        let sep = (i === 0) ? topSep : nonTopSep;
        let msg = cols.map((col, j) => col[i].padStart(widths[j])).join(sep);
        console.log(msg);
    }
}