The if statement appears exactly as it does in Java (an expression that evaluates to true or false must be included in parentheses):

    if (true or false expression)
    statement
      

The expression in parentheses is evaluated and if it is true the following statement is executed; if it is false, it is not.

Recall that the window.confirm() method returns true or false depending on whether the user clicks OK or Cancel. We will now use confirm() in an example of the if statement:

    <SCRIPT>
    var member
    member = window.confirm('Please confirm you are a member of the shopping club')
    if (member)
    window.alert('Welcome to the Shopping Club')
    </SCRIPT>
      

This code produces a confirmation dialogue box. When the user clicks OK a welcome dialogue box appears, as below.

if statements also have a matching else statement, which behaves as in Java:

    if (true or false expression)
      statement_1
    else
      statement_2
      

statement_2 is only executed if the expression in parentheses evaluates to false.