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Javascript conditional statements allow you execute certain statements depending on if a condition is met. The if...else statement is one way to do this.
The javascript code below shows you a javascript if statement.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>WebDevelopmentTutorials.com</title>
</head>
<body>
<script type="text/javascript" language="javascript">
a = 5;
if (a = 5)
{
document.write("True");
}
</script>
</body>
</html>
The javascript code above produces the text "True", because the condition is met, "a" is equal to 5.
The javascript code below shows you a javascript if...else statement.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>WebDevelopmentTutorials.com</title>
</head>
<body>
<script type="text/javascript" language="javascript">
a = 5;
b = 10;
if (a < b)
{
document.write("True");
}
else if
{
document.write("False");
}
</script>
</body>
</html>
The javascript code above produces the text "True" because the variable "a", which is equal to 5, is less than the variable "b", which is equal 10.
The javascript below displays the current time (when the page is first visited or refreshed) and produces a different greeting based on what time of the day it is and shows you a javascript if...else...else statement.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>WebDevelopmentTutorials.com</title>
</head>
<body>
<script type="text/javascript" language="javascript">
document.write("The time is: ");
now = new Date();
hours = now.getHours();
mins = now.getMinutes();
secs = now.getSeconds();
document.write(hours + ":" + mins + ":" + secs);
if (hours < 10) document.write(" Good morning");
else if (hours >= 14 && hours <= 17) document.write(" Good afternoon");
else if (hours > 17) document.write(" Good evenning");
else document.write(" Good day");
</script>
</body>
</html>
The javascript code above produces the time and greeting below.