An if statement will be executed if the if condition is true. In this code block, the variable isMailSent has been initialized with a boolean value true. Therefore, the if statement will be executed resulting a log in the console Mail sent to recipient.

An else block will be executed only if the if condition fails. In the above example, the variable isTaskCompleted has been initialized with a boolean value false. Therefore, the else block will be executed resulting in Task incomplete logging to the console.

The ! operator can be used to A) invert a Boolean value, or B) invert the truthiness of non-Boolean values. In the code block, we see how it is used in both situations.

In JavaScript, values evaluate to true or false when evaluated as Booleans. Values that will evaluate to true are known as truthy and values that evaluate to false are known as falsy. Falsy values include false, 0, empty strings, null undefined, and NaN. All other values are truthy.

JavaScript comparison operators are used to compare two values and return true or false depending on the validity of the comparison. Comparison operators include:

• strict equal (===)
• strict not equal (!==)
• greater than (>)
• less than (<)
• greater than or equal (>=)
• less than or equal (<=)

= (assign a value to something), == (check if something is equal, not strict), and === (check if something is equal, strict) are commonly confused. “Strict” means that it checks not only the equality of two values, but also the types of the two values.

Strict equality or inequality comparisons use: === and !== operators respectively. Strict comparisons evaluate the equality of the operands without employing type conversion.

Control flow statements can be chained by combining if and else statements into else if. After an initial if statement, one or more else if blocks can check additional conditions, with an optional else block to catch cases that do not match any conditional. The example above demonstrates how you can create multiple conditions in an if...else control flow statement.

The logical OR operator (||) compares two values. When it is used in a Boolean context, it returns true when either values evaluate to true. If both values evaluate to false, the || operator returns false.

Switch statements allow for compact control flow structures by evaluating a single expression and executing code blocks based on a matched case. The switch statement first evaluates the expression provided. The result of the expression is matched against one or more case clauses. If it matches one, the code inside that clause is executed. If the case clause ends with a break statement, the code inside the switch will cease executing and the next statement following switch will be executed. If no case clauses match but a default exists, the code inside default will be executed. If break is omitted from a clause (or the execution is not broken otherwise, such as returning from a function with a switch), code in subsequent clauses will continue executing until a break is encountered or the flow is otherwise broken.

The ternary operator allows for a compact syntax in the case of binary (if/else) decisions. It evaluates a single condition and executes one expression if the condition is evaluates to true and the second expression otherwise. The syntax is: condition ? expression1 : expression2. It can be read as “IF condition THEN expression1 ELSE expression2”.