Date Object and Methods

Date Object

• A useful object in the JavaScript library is the Date object.
• We now know the difference between primitive and reference types, and we know that JavaScript treats primitive types as objects(aka reference types) when using methods.
• A date object, however, needs to be declared for us to work with dates.

• We declare a date object by simply saying:

let today = new Date();

• Setting the variable equal to new Date(); constructs a new date object that the today variable is a reference to.

• There may be an instance in which you wish to create a date object that does not represent the current time. In this case, we can construct date objects like so:
• within the parenthesis, we place: (Year, Month, Day, Hour, Minute, Seconds, and Milliseconds)
• we do not have to provide all of these parameters, however.

• For example, we can provide only the year, month, and day, like so:

let myBirthday = new Date(1997, 7, 29);

• Now we can apply the many date methods to our date object, ‘today’.

Date Methods

• getFullYear : this method returns the year of the date object in a 4 digit format
  • syntax: .getFullYear()

today = new Date();
console.log("The current year is " + today.getFullYear());

myBirthday = new Date(1997, 7, 29);
console.log("I was born in " + myBirthday.getFullYear());

• 2. getMonth : this method returns the month of the date object as a number. Months begin at 0, meaning January = 0 while December = 12
  • syntax: .getMonth()

today = new Date();
console.log("The current month is " + today.getMonth());

• instances like the print statement above allow us to program our own solutions. If I wanted to print the word form of the month, such as January, we could use an array, if-else statements, or a switch statement:

let months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
let currentMonth = today.getMonth();
console.log("The current month is " + months[currentMonth]);

• 3. getDate : this method returns the day of the date object as a number from 0-31(out of the month)
  • syntax: .getDate()

today = new Date();
console.log("Today is " + today.getMonth() + " / " + today.getDate());

• 4. getDay : this method returns the day of the date object as a number from 0-6 (as a weekday)
  • syntax: .getDay()

today = new Date();
let days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
console.log("Today is " + days[today.getDay()]);

• 5. getHours : this method returns the hours of the date object as a number from 0-23
  • syntax: .getHours()

today = new Date();
console.log("The current hour is " + today.getHours());

• 6. getMinutes : this method returns the minutes of the date object as a number from 0-59
  • syntax: .getMinutes()

today = new Date();
console.log("The current minute is " + today.getMinutes());

• 7. getSeconds : this method returns the seconds of the date object as a number from 0-59
  • syntax: .getSeconds()

today = new Date();
console.log("The current second is " + today.getSeconds());
console.log("The time is now " + today.getHours() + " : " + today.getMinutes());

Exercises

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