ticktock-es/src/Factories/dateAddFactory.js

A Date utility library

export default dateAddFactory;

function dateAddFactory() {
  const parts = Object.entries({
    year: `FullYear`, month: `Month`, date: `Date`,
    day: `Date`, hour: `Hours`, minute: `Minutes`,
    second: `Seconds`, millisecond: `Milliseconds` })
    .reduce( (acc, [key, value]) =>
      ({...acc, [key]: value, [`${key}s`]: value}), {} );
  let subtract = false;
  
  const aggregateArguments = function(...argsRaw) {
    const singleArgument = argsRaw.length === 1;
    subtract = argsRaw[0].trim().startsWith(`subtract,`);

    if (subtract) {
      argsRaw = singleArgument
        ? argsRaw[0].trim().replace(/^subtract,/i, ``).split(`,`).map(v => v.trim())
        : argsRaw.filter(v => !v.startsWith(`subtract`));
    }
    
    if (singleArgument && !subtract) {
      argsRaw = argsRaw[0].split(`,`).map(v => v.trim());
    }
    
   return argsRaw
      .map( function(a) {
        if (!a) { return false; }
        const elem = a.toLowerCase().split(/ {1,}/);
        if (elem.length < 2) { return false; }
        return elem.map(v => {
            v = `${v}`.trim().replace(/[^a-z0-9-+]/g, ``);
            const num = parseInt(v, 10);
            return !Number.isNaN(num) ? subtract ? -num : +num : v;
          });
      }).filter(v => v);
  }

  return function(date, ...args) {
    if (args.length < 1) { return date; }

    let aggregated = aggregateArguments(...args);
    
    if (aggregated.length) {
      aggregated.forEach( ([n, part]) => {
          part = part;
          part = parts[part];
          if (n && part) {
            date[`set${part}`](date[`get${part}`]() + n);
          }
        }
      );
    }

    return date;
  };
}