lib/index.js
function colLetterToNumber(letters) {
    var number = 0,
        i = 0;

    for (i = 0; i < letters.length; i += 1) {
        //number += (letters.length - i - 1) * (letters.charCodeAt(i) - 64);
        number += Math.pow(26, i) * (letters.charCodeAt(letters.length - i - 1) - 64);
    }
    return number;
}
function colLetterToNumber(letters) {
    var number = 0,
        i = 0;

    for (i = 0; i < letters.length; i += 1) {
        //number += (letters.length - i - 1) * (letters.charCodeAt(i) - 64);
        number += Math.pow(26, i) * (letters.charCodeAt(letters.length - i - 1) - 64);
    }
    return number;
}
/*
converts between json and xlsx
- only the first worksheet gets converted
- cells are merged as a visual convenience but they hold no special meaning