Javascript Help

hiryuu.com · Nov 13, 2003

I have a problem...
I can seem to make a while function work

What I need is to validate the name, as long as the user inputs something everything's ok, but if the user inputs nothing, then I need a new prompt asking the user to enter his/her name.

(I know it's easier with an if statement, but the teacher wants it in a While, or do while form, and I don't get it (probably, because I haven't been going to class

).

Anyways, here's my code so far, which is wrong of course:

Code:

var name = prompt("What is your name?", "")

   	while(name==null)
   	{
   	name = prompt("Please, tell us your name, so we can serve you better:", "")
   	}

Right not it validates it the first time, but if they don't enter a name on the second prompt the loop stops

LOCOlombia · Nov 13, 2003

well, don't you want the prompt loop to stop once the name is entered, and for it to continue with the rest of the program. Let me see if I'm understading correctly, you have the loop set up now that once the name is entered correctly at the first prompt it will skip over the second part of the loop? that's how you have it set up now right?

hiryuu.com · Nov 13, 2003

Let me try to explain it :P

When you load the page, it asks you for your name, if you enter a name you go to the next question, if not then it will say: "Please, tell us your name, so we can serve you better:" as on the code above.

Now, if the user enters his name there, he goes to the next question.

That's fine untill I press cancel or I don't input a name on that second prompt, and it STILL takes me to the next question.

hiryuu.com · Nov 13, 2003

Here is the whole HTML code (well only the javascript part, everything else I took out):

Code:

<html>
<head>
 <title>A3P1: Manuel R. Medina</title>
</head>

<body>
<script language="JavaScript" type="text/javascript">
<!--
var mex = 65
var bra = 78
var quan = 100
var name = prompt("What is your name?", "")

   	while(name= "")
   	{
   	name = prompt("Please, tell us your name, so we can serve you better:", "")
   	}

var mex2 = parseInt(prompt(name + ", how many Mexico\'s jerseys do you want?", ""))

	while (isNaN(mex2) || mex2 > quan) {
	mex2 = parseInt(prompt(name + ", please enter a valid quantity (from 0 to 100).\nHow many Mexico\'s jerseys do you want?", ""))
	}

var bra2 = parseInt(prompt(name + ", how many Brazil\'s jerseys do you want?", ""))

	while (isNaN(bra2) || bra2 > quan) {
	bra2 = parseInt(prompt(name + ", please enter a valid quantity (from 0 to 100).\nHow many Brazil\'s jerseys do you want?", ""))
	}

var sum1 = mex2 * mex
var sum2 = bra2 * bra
var total = sum1 + sum2
	document.write("<hr>")
	document.write(mex2 + " Mexico\'s jersey\(s\) @ $" + mex + " =" + " $" + sum1)
	document.write("<br>")
	document.write(bra2 + " Brazil\'s jersey\(s\) @ $" + bra + " =" + " $" + sum2)
	document.write("<br>")
	document.write("Total Amount = $" + total)
	document.write("<br>")

   if(mex2 ==0 && bra2 ==0)
   {
      document.write("Thank you anyway for considering our products!");
   }
   else if(mex2 >= 1 && bra2 >= 1)
   {
      document.write("We hope you like our quality jerseys!");
   }
   else if(mex2 >= 1 || bra2 >= 1)
   {
      document.write("Next time try our other jerseys!");
   }
   if((mex2 + bra2) >= 10)
   {
      document.write("<br><b><font color=\"red\">Your order will be shipped for free!</font></b>");
   }
-->
</script>
</body>
</html>

LOCOlombia · Nov 13, 2003

Re: Re: Javascript Help

let me get my book

hiryuu.com · Nov 13, 2003

So far, I got it "working", at least now if the user press cancel it will ask again for the name (but the whole loop is a mess

).

Code:

	do
   	{
	var name = prompt("What is your name?", "")
	if(name==null)
	{	
   	name = prompt("Please, tell us your name, so we can serve you better:", "")
	}
   	} while(name==null)

Now if you go to this page: http://www.academic.rccd.cc.ca.us/~mcleod/js/class_demos/loops/do_while.html you will see a WORKING do while loop, and the code is this one:

Code:

   var input, age1;

   do 
   {
      input = prompt("Enter your age for entry to a NC-17 movie:", "");
      age1 = parseInt(input);
   
      if(isNaN(age1) || age1 < 0 || age1 > 120)
      {
         input = prompt(input + " is not a valid age! Enter your age for a NC-17 movie again:", "");
         age1 = parseInt(input);
      }

   }while(isNaN(age1) || age1 < 0 || age1 > 120)

I hope that way you could "translate" this working code to what I need, THANKS in advance.

LOCOlombia · Nov 13, 2003

Code:
Originally posted by hiryuu.com
So far, I got it "working", at least now if the user press cancel it will ask again for the name (but the whole loop is a mess ).

Code:

do { var name = prompt("What is your name?", "") if(name==null) { name = prompt("Please, tell us your name, so we can serve you better:", "") } } while(name==null)

Now if you go to this page: http://www.academic.rccd.cc.ca.us/~mcleod/js/class_demos/loops/do_while.html you will see a WORKING do while loop, and the code is this one:

Code:

var input, age1; do { input = prompt("Enter your age for entry to a NC-17 movie:", ""); age1 = parseInt(input); if(isNaN(age1) || age1 < 0 || age1 > 120) { input = prompt(input + " is not a valid age! Enter your age for a NC-17 movie again:", ""); age1 = parseInt(input); } }while(isNaN(age1) || age1 < 0 || age1 > 120)

I hope that way you could "translate" this working code to what I need, THANKS in advance.

I think I have it, its like a while loop I found in my C++ book, it goes:

do
{
it prompts user to enter age by ?
age1= input by user

if(age1 = < 0 or > 120)
{
it will prompt yuser (to enter a real age again);
age1 = user's input
}
}while (age1 < 0 > 120) repeats whole loop again.

so...

Code:

var input, name;

do
{
  input = prompt("question you want?")
  name = parseInt(input);

 if(isNaN(name) == null)
   {
    input = prompt(input + "your question again?:'','''');
    name = parseInt(input);
    {
 }while(isNan(name) == null)

your problem one the first code you posted here might have been the fact that you haden't declared the variables, you declared name as the variable but withing the body of loop, so as it wasn't expecting anything to be fill in the place of the "input" being the name, then it didn't require anything for it to go to the next question.

Now, make sure you have a second copy of your original work (code) in case this new modifications don't work.

hiryuu.com · Nov 13, 2003

Tried, won't work

I will try to make some changes, as I think you're on the right track, altought we don't have to use "IsNaN" on this case, since of course the input won't be a number (and if it was it's ok, I just need to check to see if it's blank > ask the question again).

LOCOlombia · Nov 13, 2003

sorry about the "isNaN" i'm used to dealing with C++, but its not used there either...

monkee · Nov 13, 2003

right mate, here it is:

When you are dealing with comparisons that return true or false (boolean expressions) you need to double up your =. So where you've put:

while(name="")

it should be

while(name=="") ...

LOCOlombia · Nov 13, 2003

2 == is equals

hiryuu.com · Nov 13, 2003

Originally posted by monkee
right mate, here it is:

When you are dealing with comparisons that return true or false (boolean expressions) you need to double up your =. So where you've put:

it should be

while(name=="") ...

Well duh

HAHAHAHAHAH

THANK YOU GUYS you saved my day, thank God it's due today, so I won't lose points...

THANK YOU Again, I just tested it and it works like a charm... here's the "fixed" code:

Code:

var name = prompt("What is your name?", "")

	 while(name=="")
	{	
   	name = prompt("Please, tell us your name, so we can serve you better:", "")
	}

THANK YOU

SnYper · Nov 14, 2003

I'm doing first year Comp Sci (sucks, so i'm changing majors). Anyway we're finishing off java and logic as well, and I thought I would add one thing to what someone mentioned.

== is the symbol for equivalence, which in boolean is a 3 line equal sign.

Hiryuu, i've run into the same problem a few times, it sucks how it's usually something so simple that is messing up your code.

hiryuu.com · Nov 14, 2003

Originally posted by SnYper
I'm doing first year Comp Sci (sucks, so i'm changing majors). Anyway we're finishing off java and logic as well, and I thought I would add one thing to what someone mentioned.

== is the symbol for equivalence, which in boolean is a 3 line equal sign.

Hiryuu, i've run into the same problem a few times, it sucks how it's usually something so simple that is messing up your code.

yep, the problem is ALWAYS some stupid little line, or character :crazyboy:

LOCOlombia · Nov 14, 2003

yup, haha it funny when compiling a source code, all the erros that sometimes are caused by one little misused character like you said...

SnYper · Nov 14, 2003

I was checking the replies and something came to mind that I always do to avoid that exact problem you have. When I'm comparing strings I use the x.equals("") because it'll just check the string value of the variable. Easier for me to read and understand atleast

It should work in javascript

It'd look something like this:

Code:

var name = prompt("What is your name?", "")

	 while(name.equals(""))
	{	
   	name = prompt("Please, tell us your name, so we can serve you better:", "")
	}

man united forever · Nov 14, 2003

Yeah I use the equals() method too.

Javascript Help

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