04 - If Statement

1. Start up Flash CS3 and load your Calculator example.
   
   Save the fla file with a new file name such as 04If.fla
   
   This lesson checks the calculator input and generates sensible error messages if the user enters text or negative numbers instead of valid positive numbers. The error checking is incomplete so your task is to fix this.
    
2. Modify the code in your calculator example to look like this.
   
   myButton.addEventListener(MouseEvent.CLICK, doMyCalculation);
   
   function doMyCalculation(e:MouseEvent):void
   {
       var myAnswer : Number;
   
       // Test for non numeric input (Is Not a Number isNaN)
       if (isNaN(Number(N1.text)))
       {
           myOutput.text = "The first number you entered is not valid.";
       }
       else
       // Test for negative input
       if (Number(N1.text) < 0)
       {
           myOutput.text = "The first number you entered must be positive.";
       }
       else
       // Carry out the addition (only if there were no errors).
       {
           myAnswer = Number(N1.text) + Number(N2.text);
   
           myOutput.text = String(myAnswer);
       }
   }
    
   
3. You can download 04If.fla
    
4. Here is the partially finished movie. Try entering text or negative numbers instead of normal positive numbers.
   
   
   
   
5. TASK: Complete the code above so you get sensible error messages for both the input fields.

Notes

Examples

if (counter == 0)
{
  doThis();
}

if (counter == 3)
{
  doThis();
}
else if (counter == 2)
{
  doThat();
}
else
{
  doTheOther();
}