text: $(document).ready(function(){
      $('#myAge').text('年齢：' + getAge(1998, 6, 24) + '歳');
  })
  
  /**
   * calculate age.
   * @param {number} year - birth year
   * @param {number} month - birth month
   * @param {number} day - birth day
   * @returns {number} age
   */
  function getAge(year, month, day){
    var birthday  = new Date(year, month-1, day);
    var today = new Date();
    var thisYearBirthday =
        new Date(today.getFullYear(), month-1, day);  
  
    var age = today.getFullYear() - birthday.getFullYear();
    if(today < thisYearBirthday) age -= 1;
   
    return age;
  }