Conditionals
Conditionals take an expression, which is code that evaluates to determine a value, and checks if it is true
or false
. If it’s true
, we can tell our program to do one thing — we can even account for false
to do another.
If Statement
An 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.
const isMailSent = true;if (isMailSent) {console.log('Mail sent to recipient 💌');}
The output would be:
Mail sent to recipient 💌
Note: if
is in lowercase letters. Uppercase letters will generate a JavaScript error.
Else Statement
An else
block can be added to an if block or series of if-else if blocks. The else
block will be executed only if the if
condition fails.
const isTaskCompleted = false;if (isTaskCompleted) {console.log('Task completed');} else {console.log('Task incomplete');}
If the hour
is less than 18, create a “Good day” greeting, otherwise “Good evening”:
if (hour < 18) {greeting = 'Good day 🌤';} else {greeting = 'Good evening 🌙';}
Else If Statement
After an initial if
block, 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.
If time is less than 10:00, create a “morning” greeting, if not, but time is less than 20:00, create a “day” greeting, otherwise a “Good evening”:
if (time < 10) {greeting = 'Good morning 🌄';} else if (time < 20) {greeting = 'Good day 🌁';} else {greeting = 'Good evening 🌉';}
Here, the result of greeting will be: Good day 🌁
.
Codebyte Example
What do you think will happen when pH
is changed to 7?
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