Relational and Boolean Expressions

Boolean expression is an expression that evaluates to a Boolean value (true / false) and is commonly used for conditional rendering and logic handling.
- It can be produced by relational operator, equality operators, logical NOT (!) and conditional operator (? :) (Boolean - JavaScript | MDN, n.d.).

Relational expression use relational operators and operands of various types to evaluate to some Boolean representation.

Comparison Operators:
- Used in conditional statements to compare values and take action on the result (JavaScript Comparison and Logical Operators, n.d.):

Logical Operators:
- Used to determine the logic between variables or values (JavaScript Comparison and Logical Operators, n.d.).

All relational operators return a Boolean value (Comparisons, n.d.):
- True – means “yes”, “correct” or “the truth”
- False - means “no”, “wrong”, or “not the truth”

Short Circuit Evaluation
- Short circuit evaluation (minimal evaluation) is an expression in which the result is determined without evaluating all of the operands and/or operators.
- A technique used to improve performance in Boolean expressions.
- Short-circuit evaluation in React.js allows for more concise and potentially performance-enhancing code, by ensuring that the second part of an AND (&&) operation is not evaluated if the first part is false (The Short Circuit Evaluation. And How You Cant Use It in React… | by Vitor Britto | Medium, n.d.).

Sample Code for React.js in our sample application:

Relational Expressions

Conditional Check: The if statement ensures that the selected date (clickedDate) is either today or in the future.
clickedDate >= today: A relational comparison checks if the selected date is later than or equal to the current date.
isSameDay(clickedDate, today): This additional check ensures that clicking on the current day is also valid.

Logical Expressions

The >= operator ensures that the selected date (clickedDate) is today or any future date.
The || (logical OR) ensures that if the date is the same as today (isSameDay(clickedDate, today)), the condition will still be true.
If either condition is true, the block of code inside the if statement is executed.

Boolean Expressions

The editingEvent state is used to determine whether the user is editing an existing event or adding a new one.
editingEvent ? editingEvent.id : Date.now(): If editingEvent is not null, it uses the existing event's ID; otherwise, it generates a new ID.
if (editingEvent): This block checks if editingEvent is truthy, meaning an existing event is being edited. If not, a new event is added.

Short-circuit Evaluation

Condition Check: The if (editingEvent) ensures that the code inside this block runs only if editingEvent is not null or undefined. This means the user is currently editing an existing event.
Logic Inside: When editingEvent exists, the app updates the events array by replacing the existing event with the updated one (newEvent).