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
|| checks two values and returns a boolean. If one or both values are truthy, it returns
true. If both values are falsy, it returns
The ternary operator allows for a compact syntax in the case of binary (choosing between two choices) decisions. It accepts a condition followed by a
? operator, and then two expressions separated by a
:. If the condition evaluates to truthy, the first expression is executed, otherwise, the second expression is executed. It can be read as “IF condition THEN expression1 ELSE expression2”.
else block is added to an
if block or series of
else if blocks. The
else block will be executed only if the
if condition fails.
The logical AND operator
&& checks two values and returns a boolean. If both values are truthy, then it returns
true. If one, or both, of the values is falsy, then it returns
switch statements provide a means of checking an expression against multiple values. It first evaluates an expression. The result of the expression is matched against values in one or more
case clauses. If a case matches, the code inside that clause is executed.
case clause should finish with a
break keyword. If no case matches but a
default clause is included, the code inside
default will be executed. If
break is omitted from the block of a
case (or the execution is not broken otherwise, such as returning from a function with a switch), the
switch statement will continue to check against
case values until a break is encountered or the flow is broken.
if statement accepts an expression with a set of parentheses
- If the expression evaluates to a truthy value, then the code within its code body executes.
- If the expression evaluates to a falsy value, its code body will not execute.
The strict equality operator (
===) checks if two values are the same and returns
true if they are the same. The inequality comparison operator (
!==) check if two values are different and return
true if they aren’t the same.
! operator can be used to do one of the following:
- Invert a Boolean value.
- Invert the truthiness of non-Boolean values.
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 (
else if Statement
else if Statement
After an initial
else if blocks can each check an additional condition. An optional
else block can be added after the
else if block(s) to run by default if none of the conditionals evaluated to truthy.
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.
- 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 binar…
Magic Eight Ball
Design the logic for an app that will give runners information on race day!