Parsing & Performance about date-and-time HOT 9 CLOSED

// Load "date-and-time" module.
const date = require('date-and-time');

// This is a compile function. The function name might be change.
date.compile = function (formatString) {
    var re = /([A-Za-z])\1*|./g, keys, pattern = [formatString];

    formatString = formatString.replace(/\[[^\[\]]*]|\[.*\][^\[]*\]/g, function (str) {
        return str.replace(/./g, ' ').slice(2);
    });
    while ((keys = re.exec(formatString))) {
        pattern[pattern.length] = keys[0];
    }
    return pattern;
};

// Rewrite the preparse function.
date.preparse = function (dateString, arg) {
    var parser = locales[lang].parser, token, result, offset = 0,
        pattern = typeof arg === 'string' ? date.compile(arg) : arg, formatString = pattern[0],
        dt = { Y: 1970, M: 1, D: 1, H: 0, A: 0, h: 0, m: 0, s: 0, S: 0, _index: 0, _length: 0, _match: 0 };

    dateString = parser.pre(dateString);
    for (var i = 1, len = pattern.length; i < len; i++) {
        token = pattern[i];
        if (parser[token]) {
            result = parser[token](dateString.slice(offset), formatString);
            if (!result.length) {
                break;
            }
            offset += result.length;
            dt[token.charAt(0)] = result.value;
            dt._match++;
        } else if (token === dateString.charAt(offset) || token === ' ') {
            offset++;
        } else {
            break;
        }
    }
    dt.H = dt.H || parser.h12(dt.h, dt.A);
    dt._index = offset;
    dt._length = dateString.length;
    return dt;
};

const pattern = date.compile('MMM. D YYYY h:m:s A');

date.parse('Nov. 6 2019 1:11:11 p.m.', pattern);
date.parse('Nov. 6 2019 2:22:22 p.m.', pattern);
date.parse('Nov. 6 2019 3:33:33 p.m.', pattern);

// dummy lambda function
{
  const pattern = date.compile('MMM. D YYYY h:m:s A');
  const many_results = [];

  for (const dateString of many_date_string) {
    many_results.push(date.parse(dateString, pattern));
  }
  return many_results;
}

// dummy lambda function
{
    const pattern = date.compile('MMM. D YYYY h:m:s A');

    save_somewhere(JSON.stringify(pattern));  // pseudo code
}

// dummy lambda function
{
    const pattern = JSON.parse(load_from_somewhere(pattern));  // pseudo code

    return date.parse(dateString, pattern);
}