if statements and the like) alter control flow by only executing blocks of code if certain condition(s) are met. These structures essentially allow a program to make decisions about which code is executed as the program runs.
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
|| operator returns
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”.
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.
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.
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.
Strict equality or inequality comparisons use
!== operators respectively. Strict comparisons evaluate the equality of the operands without employing type conversion.
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
0, empty strings,
NaN. All other values are truthy.
! operator can be used to A) invert a Boolean value, or B) invert the truthiness of non-Boolean values. In the above code block, we see how it is used in both situations.
false depending on the validity of the comparison. Comparison operators include strict equal (
===), strict not equal (
!==), greater than (
>), less than (
<), greater than or equal (
>=), and 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.
if...else Control Flow Statements
if...else Control Flow Statements
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.
- 1In life, we make decisions based on circumstances. Think of an everyday decision as mundane as falling asleep— if we are tired, we go to bed, otherwise, we wake up and start our day. These i…
- 2We often perform a task based on a condition. For example, if the weather is nice today, then we will go outside. If the alarm clock rings, then we’ll shut it off. If we’re tired, then we’ll go to …
- 3In the previous exercise, we used an if statement that checked a condition to decide whether or not to run a block of code. In many cases, we’ll have code we want to run if our condition evaluates …
- 4When writing conditional statements, sometimes we need to use different types of operators to compare values. These operators are called comparison operators. Here is a list of some handy compar…
- 6Let’s consider how non-boolean data types, like strings or numbers, are evaluated when checked inside a condition. Sometimes, you’ll want to check if a variable exists and you won’t necessarily w…
- 7Truthy and falsy evaluations open a world of short-hand possibilities! Say you have a website and want to take a user’s username to make a personalized greeting. Sometimes, the user does not hav…
- 8In the spirit of using short-hand syntax, we can use a ternary operator to simplify an if…else statement. Take a look at the if…else statement example: let isNightTime = true; if (isNightT…
- 9We can add more conditions to our if…else with an else if statement. The else if statement allows for more than two possible outcomes. You can add as many else if statements as you’d like, to mak…
- 10else if statements are a great tool if we need to check multiple conditions. In programming, we often find ourselves needing to check multiple values and handling each of them differently. For exam…
- 11Way to go! Here are some of the major concepts for conditionals: An if statement checks a condition and will execute a task if that condition evaluates to true. if…else statements make binary…
Magic Eight Ball
Design the logic for an app that will give runners information on race day!