sample.js

        var timeSyntaxRules = {

          1: function (time) {
            // Check to see if first digit is not 1, then preface it with zero
            var pattern = /[2-9]/;

            if (time.match(pattern)) {
              return "0" + time;
            }

            return time;
          },

          3: function (time) {
            if (time[2] === ':') {
              return time.substring(0, 2);
            }

            return time
          },

          4: function (time) {
            // Edit time string if user is trying to input a 1:XX style time
            if (time[3] === 'A' || time[3] === 'P') {
              return "0" + time.substring(0, 3) + time.substring(3);
            }

            return time;
          },

          5: function (time) {
            if (time[4] === ' ') {
              return time.substring(0, 4);
            }

            return time;
          },

          /**
           * Insert a given value into a position in a string
           *
           * @param  {string}     str     The string you want manipulated
           * @param  {int}        pos     The position in the string you want the value inserted at
           * @param  {string}     val     The value you want inserted at that position
           * @return {return}             An updated string with the value inserted
           */
          insert: function (str, pos, val) {
            return [str.substring(0, pos) + val + str.substring(pos)].join('');
          }
        };
        
        /**
         * Formats the given time according to our timepicker syntax rules
         * @param  {string} time    The time we want to format
         * @return {string}         The formatted string
         */
        function formatTime(time) {
          // Strip our time of any backslashes that would escape our RegEx sequence
          time = time.replace(/\\/g, '');

          // Split up the string into individual characters
          var letters = time.toUpperCase().split('');

          // Format the string from the beginning in order to ensure each syntax rule is enforced
          return letters.reduce(function (prev, curr) {
            return applySyntaxRules(prev + curr, timeSyntaxRules);
          }, "");
        };

        /**
         * Apply a given set of syntax rules to a string
         * @param  {string} str     The string that's going to be formatted
         * @param  {object} rules   A dictionary object applied to the given string
         * @return {string}         The formatted string
         */
        function applySyntaxRules(str, rules) {
          // Apply the syntax rule if we have one for the given time length
          if (rules[str.length]) {
            str = rules[str.length](str);
          }

          return str;
        };