Check time format and transfer 12-hour to 24-hour format

check_time_format.js

/* The original source: http://www.the-art-of-web.com/javascript/validate-date/  */


//obj is JQuery object
// return : true -- time invalid, false -- time valid

function checkTime(obj){

  var errorFlag = false;
  re = /^(\d{1,2}):(\d{2})(:00)?([apAP][mM])?$/; 

  if (regs = obj.val().match(re)){
    if(regs[4]){  
      //12-hour time format with am/pm
      if (regs[1]<1 || regs[1]>12){
        errorFlag = true;
      }
      if (regs[4].toLowerCase() == 'am' && regs[1] == 12 ){ //Need convert 12-hour to 24-hour
        regs[1]= '00';
      }else if(regs[4].toLowerCase() =='pm' && regs[1]<12){
        regs[1] = parseInt(regs[1])+12;
      }
      obj.val([regs[1],':',regs[2]].join(''));
    }else{
      //24-hour time format
      if(regs[1]>23){
          errorFlag = true;
      }
    }
    if( regs[2]>59){
      errorFlag = true;
    }
  }else{
    errorFlag = true;
  }
  return errorFlag;
}