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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
<h1>JavaScript If...Else Statements</h1>
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<p class="intro">Conditional statements in JavaScript are used to perform different actions based on different conditions.</p>
<hr />
<h2>Examples</h2>
<p><a target="_blank" href="tryit.asp@filename=tryjs_ifthen">If statement</a><br />
How to write an if statement.</p>
<p><a target="_blank" href="tryit.asp@filename=tryjs_ifthenelse">If...else statement</a><br />
How to write an if...else statement.</p>
<p><a target="_blank" href="tryit.asp@filename=tryjs_elseif">If..else if...else statement</a><br />
How to write an if..else if...else statement.</p>
<p><a target="_blank" href="tryit.asp@filename=tryjs_randomlink">Random link</a><br />
This example demonstrates a link, when you click on the link it will take
you to W3Schools.com OR to RefsnesData.no. There is a 50% chance for each of
them.</p>
<hr />
<h2>Conditional Statements</h2>
<p>Very often when you write code, you want to perform different actions for
different decisions. You can use conditional statements in your code to do this.</p>
<p>In JavaScript we have the following conditional statements:</p>
<ul>
<li><b>if statement</b> - use this statement if you want to execute some
code only if a specified condition is true</li>
<li><b>if...else statement</b> - use this statement if you want to execute some code if
the condition is true and another code if the condition is false</li>
<li><b>if...else if....else statement</b> - use this statement if you want
to select one of many blocks of code to be executed</li>
<li><b>switch statement</b> - use this statement if you want to select one of
many blocks of code to be executed</li>
</ul>
<hr />
<h2>If Statement</h2>
<p>You should use the if statement if you want to execute some code only if a
specified condition is true.</p>
<h3>Syntax</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<td>
<pre>if (<i>condition</i>)
{
<i>code to be executed if condition is true</i>
}</pre>
</td>
</tr>
</table>
<p>Note that if is written in lowercase letters. Using uppercase letters (IF) will
generate a JavaScript error!</p>
<h3>Example 1</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<td>
<pre><script type="text/javascript">
//Write a "Good morning" greeting if
//the time is less than 10</pre>
<pre>var d=new Date();
var time=d.getHours();
if (time<10)
{
document.write("<b>Good morning</b>");
}
</script></pre>
</td>
</tr>
</table>
<h3>Example 2</h3>
<table class="ex" cellspacing="0" border="1" width="100%" id="table5">
<tr>
<td>
<pre><script type="text/javascript">
//Write "Lunch-time!" if the time is 11</pre>
<pre>var d=new Date();
var time=d.getHours();
if (time==11)
{
document.write("<b>Lunch-time!</b>");
}
</script></pre>
</td>
</tr>
</table>
<p><b>Note:</b> When <b>comparing</b> variables you must always use two equals
signs next to each other (==)!</p>
<p>Notice that there is no ..else.. in this syntax. You just tell the code to
execute some code <b>only if the specified condition is true</b>.</p>
<hr />
<h2>If...else Statement</h2>
<p>If you want to execute some code if a condition is true and another code if
the condition is not true,
use the if....else statement.</p>
<h3>Syntax</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<td>
<pre>if (<i>condition</i>)
{
<i>code to be executed if condition is true</i>
}
else
{
<i>code to be executed if condition is not true</i>
}</pre>
</td>
</tr>
</table>
<h3>Example</h3>
<table class="ex" cellspacing="0" border="1" width="100%">
<tr>
<td>
<pre><script type="text/javascript">
//If the time is less than 10,
//you will get a "Good morning" greeting.
//Otherwise you will get a "Good day" greeting.</pre>
<pre>var d = new Date();
var time = d.getHours();
if (time < 10)
{
document.write("Good morning!");
}
else
{
document.write("Good day!");
}
</script></pre>
</td>
</tr>
</table>
<br />
<hr />
<h2>If...else if...else Statement</h2>
<p>You should use the if....else if...else statement if you want to select one
of many sets of lines to execute.</p>
<h3>Syntax</h3>
<table class="ex" cellspacing="0" border="1" width="100%" id="table3">
<tr>
<td>
<pre>if (<i>condition1</i>)
{
<i>code to be executed if condition1 is true</i>
}
else if (<i>condition2</i>)
{
<i>code to be executed if condition2 is true</i>
}
else
{
<i>code to be executed if condition1 and
condition2 are not true</i>
}</pre>
</td>
</tr>
</table>
<h3>Example</h3>
<table class="ex" cellspacing="0" border="1" width="101%" id="table4">
<tr>
<td>
<pre><script type="text/javascript">
var d = new Date()
var time = d.getHours()
if (time<10)
{
document.write("<b>Good morning</b>");
}
else if (time>10 && time<16)
{
document.write("<b>Good day</b>");
}
else
{
document.write("<b>Hello World!</b>");
}
</script></pre>
</td>
</tr>
</table>
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