Constants

• Alright now let's declare a variable called interest rate

let interestRate = 0.3;

• Now this is the initial value, we can always change that later, so, we can set interest rate to let's say 1

let interestRate = 0.3;
interestRate = 1;

• Now if you log this on the console, of course we're going to see the new value, right? So save the changes, and here's one on the console.

• However, on a real world application, there are situations that we don't want the value of a variable to change.

• Because otherwise it's going to create all kinds of bugs in our application.

• In those situations, instead of a variable, we use a constant.

Remember that the value of a variable as the name implies, can change, but the value of a constant cannot change.

Syntax:

• So here, if we change let to const. Now interestRate will be constant.

const interestRate = 0.3;
interestRate = 1;

• So, when I save the changes, we're going to see an error, in the console on line 2, where we reassign interestRate.

• So we cannot reassign a constant or change the value of the constant variable.

• The best practice is that if you are not going to reassign the value to variable then you should you constant variable (const keyword) and that should be the default choice. Otherwise, use variable (let keyword).