The if Statement

The if construct is a control statement. It controls the program flow based on a logical expression that evaluates either to true or false.

The structure of an if statement is as follows:

if (expression)
{
     statement;
}

The statement is executed only if the expression evaluates to true.

Example

The following example sends the value selected in the form to the checkOptions( ) function. The function contains three if statements that check whether the passed value is 1, 2, or 3, respectively. If the condition evaluates to true, it enters the statement block and executes the enclosed print statement.

1
2
3

The Function Call

<form action="javascript:;" method="post" id="form1">
<select name="selectGroup">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br /><br />
<input type="button" name="button1" value="Submit" onclick="checkOptions(selectGroup[selectGroup.selectedIndex].value)">
</form>

The Function Code

<script type="text/javascript">
<!--
  function checkOptions(selectedValue)
  {     
    document.write("<p>Checking option 1");
    if (selectedValue == 1)
    {
      document.write("<p>1 = 1\nFound match.");
    }
  
    document.write("<p>Checking option 2");
    if (selectedValue == 2)
    {
      document.write("<p>2 = 2\nFound match.");
    }
  
    document.write("<p>Checking option 3");
    if (selectedValue == 3)
    {
      document.write("<p>3 = 3\nFound match.");
    }
    document.close();
  }
//-->
</script>