Here's the first code:
<script type="text/vbsscript">
Option Explicit
DIM Firstnumber, secondnumber, answer
firstnumber = inputbox("what is the first number")
secondnumber = inputbox("What is the second number")
answer = firstnumber + secondnumber
document.write "The answer is " & answer
</script>
When I hit the preview button it looked like this:
When you get a blank screen with no errors then the problem is in the first or last lines of script. Notice that the first line of script is:
<script type="text/vbsscript"> <-- the extra "s" in vbscipt is causing the problem.
So, if you get a blank screen with no error message recheck the first and last lines of script to ensure they are correct.
Next problem: Here's my code:
<script type="text/vbscript">
Option Explicit
DIM Firstnumber, secondnumber, answer
firstnumber = inputbox("what is the first number) '<-- Missing quote
(")after the text first number
secondnumber = inputbox("What is the second number")
answer = firstnumber + secondnumber
document.write "The answer is " & answer
</script>
This is the error I get:
You can see that it says "Unterminated String Constant". A string constant is just some text. In programming we call a bunch of text characters a "string". It says it's unterminated which means that we have a start quote, starting the text but we didn't place an end quote to stop the text. It says that the error is on line 4. Which you can see is true if you count the lines of code above. That's why you shouldn't ignore these messages. They are telling you exactly where your error is and what type of error you made.
Here's my code again:
<script type="text/vbscript">
Option Explicit
DIM Firstnumber, secondnumber, answer
firstnumber = inputbox("what is the first number")
secondnumber = inputbox("What is the second number")
answer = firstnumber + secondnumber
document.write "The answer is " & ansswer '
<---answer is misspelled
</script>
When I run the code I get the error below:
Variable undefined means that Option Explicit is working and you used a place in memory that you didn't declare in the DIM line. Be careful, don't just add that to the DIM line because it's more likely that you misspelled it in your code. It says that on line 7 "ansswer" is not in the DIM line. Sure enough, "answer" is on the DIM line so I have to change ansswer to answer and everything works fine.
Here's another common error where I've placed a space in a variable name:
<script type="text/vbscript">
Option Explicit
DIM Firstnumber, secondnumber, theanswer
firstnumber = inputbox("what is the first number")
secondnumber = inputbox("What is the second number")
answer = firstnumber + secondnumber
document.write "The answer is " & the answer '<-- I used "the
answer" instead of "theanswer". Variable names can not have spaces in
them.
</script>
This is the error message:
Expected end of statement: Notice it doesn't say anything about a bad variable name, that's because the error is just the space. It knows that after the word "the" there should be anything (end of statement) and it sees the word "answer". You will see this error message when you leave off operators (+, - ,/ ,*).
Joining instead of adding error: The last type of typical problem you'll see is where your code joins numbers together instead of adding them together. When I run the following code and use 5 as the first number and 6 as the second number the output will be 56 instead of 11.
<script type="text/vbscript">
Option Explicit
DIM Firstnumber, secondnumber, theanswer
firstnumber = inputbox("what is the first number")
secondnumber = inputbox("What is the second number")
theanswer = firstnumber + secondnumber
document.write "The answer is " & theanswer
</script>
The reason this happens is that the plus symbol (+) in programming means both "join" and "add". If there are two pieces of text then it joins them, there are two numbers then it adds. So, what's the problem here. I typed in the number 5 and the number 6 so why did it join them together?
The problem is the inputbox() function. When you type in the 5 it doesn't store the binary five (00000101) it stores the ASCII (text) value of five (00110101) as per the ASCII chart in lesson 2. Same when you type 6 for the second inputbox(). It stores the ASCII value of six instead of the binary value of six. So, when html kit evaluates the line theanwer = firstnumber + secondnumber it uses the + sign as a join symbol because there are two pieces of text. Fortunately, there's a way to fix this so we can add those numbers. We use a function called Cint(). Cint stands for "change into an interger". Whatever is in the () is changed to a number. So our code is changed to this: theanswer = cint(firstnumber) + secondnumber. When we do this the answer comes out 11. What if we did this theanswer = cint(firstnumber + secondnumber) ? Well the answer would come out 56. That's because it would join 5 and 6 then turn it into a number. We only need to change the first variable into a number for the plus sign to be interpreted as addition rather than joining.
The joining instead of adding issue will come up over and over again during this class so be aware of it. This is another reason for you to NOT use complex math in your equations. You won't be able to test parts of the equation when it's complex.