how to code a check age function in javascript
function Person(dob) { // [1] new Date(dateString) this.birthday = new Date(dob); // transform birthday in date-object this.calculateAge = function() { // diff = now (in ms) - birthday (in ms) // diff = age in ms const diff = Date.now() - this.birthday.getTime(); // [2] new Date(value); -> value = ms since 1970 // = do as if person was born in 1970 // this works cause we are interested in age, not a year const ageDate = new Date(diff); // check: 1989 = 1970 + 19 console.log(ageDate.getUTCFullYear()); // 1989 // age = year if person was born in 1970 (= 1989) - 1970 = 19 return Math.abs(ageDate.getUTCFullYear() - 1970); }; } var age =new Person('2000-1-1').calculateAge(); console.log(age); // 19