Time Parsing

parseHoursAndMinutes.js

function parseHoursAndMinutes(input) {

  if (typeof input !== "string") {
    throw "Time must be a string";
  }
  
  input = input.toLowerCase().trim();
  
  if (input.length === 0) {
    throw "Time must not be empty";
  }
  
  var hours = 0;
  var minutes = "00";
  var parts = input.split(":");
  
  hours = parseInt(parts[0],10);
  
  if (isNaN(hours)) {
    throw "Cannot parse '"+ input +"'";
  }

  if (hours < 0) {
    throw "Hours must be greater than zero";
  }
  
  if (hours > 23) {
    throw "There are not that many hours in a day";
  }
  
  if (hours <= 12 &&  /pm?$/i.test(input)) {
    hours += 12;
  }
  
  if (parts.length > 1) {
    minutes = parseInt(parts[1],10);
    
    if (isNaN(minutes)) {
      minutes = 0;   
    }
    
    if (minutes > 59) {
      throw "There are only 60 minutes in an hour";
    }
    
    if (minutes < 0) {
      throw "Minutes must be greater than zero";
    }
  }
  
  return {
    hours: hours,
    minutes: minutes
  };
}

usage.js

var cases = [
  "1p", "00:59", "23:14", "5:30",
  "11:59 pm", "12AM", "11a", "notatime"
];


cases.forEach(function(item) {
  var result;
  var d;
  try {
    
    // parse it
    result = parseHoursAndMinutes(item); 
    
    // Create a new moment and set hours and minutes
    d = moment().hours(result.hours).minutes(result.minutes);
    
    // print it
    console.log(d.format("h:mm a"));
    
   } catch(err) {
    console.error(err);
  }
});