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<title>JavaScript Comparison and Logical Operators</title>
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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
<h1>JavaScript Comparison and Logical Operators</h1>
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<p class="intro">Comparison and Logical operators are used to test for true or
false.</p>
<hr />
<h2>Comparison Operators</h2>
<p>Comparison operators are used in logical statements to determine equality or
difference between variables or values. </p>
<p>Given that <b>x=5</b>, the table below explains the comparison operators:</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table1">
<tr>
<th width="15%" align="left">Operator</th>
<th width="45%" align="left">Description</th>
<th width="40%" align="left">Example</th>
</tr>
<tr>
<td valign="top">==</td>
<td valign="top">is equal to
</td>
<td valign="top">x==8 is false
</td>
</tr>
<tr>
<td valign="top">===</td>
<td valign="top">is exactly equal to (value and type)</td>
<td valign="top">x===5 is true<br />
x==="5" is false</td>
</tr>
<tr>
<td valign="top">!=</td>
<td valign="top">is not equal
</td>
<td valign="top">x!=8 is true
</td>
</tr>
<tr>
<td valign="top">></td>
<td valign="top">is greater than
</td>
<td valign="top">x>8 is false
</td>
</tr>
<tr>
<td valign="top"><</td>
<td valign="top">is less than
</td>
<td valign="top">x<8 is true</td>
</tr>
<tr>
<td valign="top">>=</td>
<td valign="top">is greater than or equal to
</td>
<td valign="top">x>=8 is false</td>
</tr>
<tr>
<td valign="top"><=</td>
<td valign="top">is less than or equal to
</td>
<td valign="top">x<=8 is true</td>
</tr>
</table>
<br />
<hr />
<h2>How Can it be Used</h2>
<p>Comparison operators can be used in conditional statements to compare values
and take action depending on the result:</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table7">
<tbody>
<tr>
<td>
<pre>if (age<18) document.write("Too young");</pre>
</td>
</tr>
</tbody>
</table>
<p>You will learn more about the use of
conditional statements in the next chapter of this tutorial.</p>
<hr />
<h2>Logical Operators</h2>
<p>Logical operators are used in determine the logic between variables or
values.</p>
<p>Given that <b>x=6 and y=3</b>, the table below explains the logical
operators: </p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table2">
<tr>
<th width="15%" align="left">Operator</th>
<th width="45%" align="left">Description</th>
<th width="40%" align="left">Example</th>
</tr>
<tr>
<td valign="top">&&</td>
<td valign="top">and
</td>
<td valign="top"> (x < 10 && y > 1) is true</td>
</tr>
<tr>
<td valign="top">
||</td>
<td valign="top">or
</td>
<td valign="top"> (x==5 || y==5) is false</td>
</tr>
<tr>
<td valign="top">
!</td>
<td valign="top">not
</td>
<td valign="top"> !(x==y) is true</td>
</tr>
</table>
<br />
<hr />
<h2>Conditional Operator</h2>
<p>JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.</p>
<h3>Syntax</h3>
<table class="ex" cellspacing="0" border="1" width="100%" id="table5">
<tbody>
<tr>
<td>
<pre>variablename=(condition)?value1:value2 </pre>
</td>
</tr>
</tbody>
</table>
<h3>Example</h3>
<table class="ex" cellspacing="0" border="1" width="100%" id="table6">
<tbody>
<tr>
<td>
<pre>greeting=(visitor=="PRES")?"Dear President ":"Dear ";</pre>
</td>
</tr>
</tbody>
</table>
<p>If the variable <b>visitor</b> has the value of "PRES", then the variable <b>
greeting</b> will be assigned the value "Dear
President " else it will be assigned "Dear".</p>
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