Read this tutorial and learn useful information about declaring a constant by using the const keyword which creates a read-only reference to the value.
Read this tutorial and learn about the safe method of calling a function when you have its name as a string. Also, read about why you should not use eval().
The tutorial provides information of getting the current date, time and both by running a simple piece of code. Also, get the full explanation of the code.
Read the tutorial and learn the methods of getting the value of the selected option in a select box using jQuery. Read about the text() and val() methods.