Table of Contents
How to Write Conditional Statements in JavaScript
1. If Statement
This statement is used to execute some code only if a specified condition is true. It was the most basic conditional statement used in JavaScript. It takes only a single condition in order to execute the statement. If the specified condition matches, it will execute the statement; otherwise, it won’t be executed.
Read Also: How to Write JavaScript With HTML?
Syntax:
The following is the syntax for using an if statement in JavaScript.
if {condition}{
code to be executed if condition is true
}Example:
The following JavaScript code gets the system date and extracts only the hours from it. Then the statement checks whether the extracted value of the hour is less than 10 and executes the statement if the condition is true.
<script type="text/javascript">
var d=new Date()
var time=d.getHours()
if (time<10){
document.write("<b>Good morning</b>")
}
</script>Preview:
This script writes “Good morning” greeting only when the time is less than 10
Read Also: How to Loop Using JavaScript?
2. If … else statement
There is another conditional statement in JavaScript that takes two conditions. This statement is used to execute some code only if the condition is true and another code if the condition is false.
Syntax:
The following is the syntax for using the if … else statement in JavaScript.
if {condition}
{
code to be executed if condition is true
}
else {
code to be executed if condition is not true
}Example:
The following JavaScript code gets the system date and extracts only the hours from it. Then the if … else statement checks whether the extracted value of the hour is less than 10. If it is less than 10, it writes “Good morning,” otherwise it writes “Good day.”
<script type="text/javascript">
var d=new Date()
var time=d.getHours()
if (time<10)
{
document.write("Good morning")
}
else {
document.write("Good Day")
}
</script>Preview:
The following is the preview of executing the JavaScript code given above.
Read Also: How to Create Changeable Date and Time Using JavaScript?
3. Switch statement
This statement is used to select one of many blocks of code to be executed based on the condition provided.
Syntax:
The following is the syntax for using switch statements in JavaScript.
switch(n) {
case 1:
execute code block 1
break;
case 2:
execute code block 2
break;
default:
code to be executed if n is different from case 1 and 2
}Example:
The following JavaScript code gets the system date and extracts only the weekday value from it. Then the switch statement writes "Good Friday" if the day value is 5, writes "Super Saturday" if the day value is 6, and writes "Sleepy Sunday" if the day value is 0. Lastly, the switch statement writes "I am looking forward to this weekend!" if none of the conditions match.
<script type="text/javascript">
var d=new Date();
theDay=d.getDay();
switch(theDay) {
case 5:
document.write("Good Friday");
break;
case 6:
document.write("Super Saturday");
break;
case 0:
document.write("Sleepy Sunday");
break;
default:
document.write("I am looking forward to this weekend!");
}</script>Preview:
The following is the preview of executing the JavaScript code given above.
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