vue-moment.js

module.exports = {
  install(Vue, options) {
    const moment = options && options.moment ? options.moment : require('moment');

    Object.defineProperties(Vue.prototype, {
      $moment: {
        get() {
          return moment;
        },
      },
    });

    Vue.moment = moment;

    Vue.filter('moment', (...args) => {
      args = Array.prototype.slice.call(args);
      const input = args.shift();
      let date;

      if (Array.isArray(input) && typeof input[0] === 'string') {
        // If input is array, assume we're being passed a format pattern to parse against.
        // Format pattern will accept an array of potential formats to parse against.
        // Date string should be at [0], format pattern(s) should be at [1]
        date = moment(input[0], input[1], true);
      } else if (typeof input === 'number') {
        if (input.toString().length < 12) {
          // If input is an integer with fewer than 12 digits, assume Unix seconds...
          date = moment.unix(input);
        } else {
          // ..otherwise, assume milliseconds.
          date = moment(input);
        }
      } else {
        // Otherwise, throw the input at moment and see what happens...
        date = moment(input);
      }

      if (!input || !date.isValid()) {
        // Log a warning if moment couldn't reconcile the input. Better than throwing an error?
        console.warn('Could not build a valid `moment` object from input.');
        return input;
      }

      function parse(...args) {
        args = Array.prototype.slice.call(args);
        const method = args.shift();

        switch (method) {
          case 'add': {
            /*
            * Mutates the original moment by adding time.
            * http://momentjs.com/docs/#/manipulating/add/
            */

            const addends = args.shift()
              .split(',')
              .map(Function.prototype.call, String.prototype.trim);
            const obj = {};

            for (let n = 0; n < addends.length; n++) {
              const addend = addends[n].split(' ');
              obj[addend[1]] = addend[0];
            }
            date.add(obj);
            break;
          }

          case 'subtract': {
            /*
            * Mutates the original moment by subtracting time.
            * http://momentjs.com/docs/#/manipulating/subtract/
            */

            const subtrahends = args.shift()
              .split(',')
              .map(Function.prototype.call, String.prototype.trim);
            const obj = {};

            for (let n = 0; n < subtrahends.length; n++) {
              const subtrahend = subtrahends[n].split(' ');
              obj[subtrahend[1]] = subtrahend[0];
            }
            date.subtract(obj);
            break;
          }

          case 'from': {
            /*
            * Display a moment in relative time, either from now or from a specified date.
            * http://momentjs.com/docs/#/displaying/fromnow/
            */

            let from = 'now';
            let removeSuffix = false;

            if (args[0] === 'now') args.shift();
            // If valid, assume it is a date we want the output computed against.
            if (moment(args[0]).isValid()) from = moment(args.shift());

            if (args[0] === true) {
              args.shift();
              removeSuffix = true;
            }

            if (from !== 'now') {
              date = date.from(from, removeSuffix);
            } else {
              date = date.fromNow(removeSuffix);
            }
            break;
          }

          case 'diff': {
            /*
            * Mutates the original moment by doing a difference with another date.
            * http://momentjs.com/docs/#/displaying/difference/
            */

            let referenceTime = moment();
            let units = '';
            let float = false;

            if (moment(args[0]).isValid()) {
              // If valid, assume it is a date we want the output computed against.
              referenceTime = moment(args.shift());
            } else if (args[0] === null || args[0] === 'now') {
              // If null or 'now', remove argument and proceed with default referenceTime.
              args.shift();
            }

            if (args[0]) units = args.shift();

            if (args[0] === true) float = args.shift();

            date = date.diff(referenceTime, units, float);
            break;
          }

          case 'calendar': {
            /*
            * Formats a date with different strings depending on how close
            * to a certain date (today by default) the date is.
            * http://momentjs.com/docs/#/displaying/calendar-time/
            */

            let referenceTime = moment();
            let formats = {};

            if (moment(args[0]).isValid()) {
              // If valid, assume it is a date we want the output computed against.
              referenceTime = moment(args.shift());
            } else if (args[0] === null || args[0] === 'now') {
              // If null or 'now', remove argument and proceed with default referenceTime.
              args.shift();
            }

            if (typeof args[0] === 'object') formats = args.shift();

            date = date.calendar(referenceTime, formats);
            break;
          }

          case 'utc': {
            /*
            * Mutates the original moment by converting to UTC
            * https://momentjs.com/docs/#/manipulating/utc/
            */
            date.utc();
            break;
          }

          case 'timezone': {
            /*
            * Mutates the original moment by converting to a new timezone.
            * https://momentjs.com/timezone/docs/#/using-timezones/converting-to-zone/
            */
            date.tz(args.shift());
            break;
          }

          default: {
            /*
            * Formats a date by taking a string of tokens and replacing
            * them with their corresponding values.
            * http://momentjs.com/docs/#/displaying/format/
            */

            const format = method;
            date = date.format(format);
          }
        }

        if (args.length) parse.apply(parse, args);
      }

      parse.apply(parse, args);

      return date;
    });

    Vue.filter('duration', (...args) => {
      /*
      * Basic pass-through filter for leveraging moment.js's ability
      * to manipulate and display durations.
      * https://momentjs.com/docs/#/durations/
      */
      args = Array.prototype.slice.call(args);
      const input = args.shift();
      const method = args.shift();

      function createDuration(time) {
        if (!Array.isArray(time)) time = [time];
        const result = moment.duration(...time);
        if (!result.isValid()) console.warn('Could not build a valid `duration` object from input.');
        return result;
      }
      let duration = createDuration(input);

      if (method === 'add' || method === 'subtract') {
        // Generates a duration object and either adds or subtracts it
        // from our original duration.
        const durationChange = createDuration(args);
        duration[method](durationChange);
      } else if (duration && duration[method]) {
        // This gives a full proxy to moment.duration functions.
        duration = duration[method](...args);
      }

      return duration;
    });
  },
};