JavaScript Help

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stinger608

Joined: December 5, 2008 Status: Offline Posts: 169 Rep:

JavaScript Help

Wed Oct 27, 2010 10:05:22 PM #138322 Perm Link

Hey everyone, just getting started in JavaScript, and basically it is kicking my butt so far. It seems that the class is more for an intermediate learner than a beginner

None the less, I have this assignment due, and many of us students are completely in the dark here. LOL Anyhow, this is the question we must answer.

Write JavaScript code that anticipates and handles an error for an expected numeric field. This code is executed on keypress and the entered value is saved for you in a variable called enteredChar. Include the try block of JavaScript statements needed to check if the character is not a number or a non-alphanumeric character or if you throw an error message.

Any help would be much appreciate

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Tornado

Retro Grade Joined: August 16, 2003 Status: Offline Posts: 2958 Rep:

(No Title)

Wed Oct 27, 2010 11:48:03 PM #138324 Perm Link

In response to stinger608 #138322

I haven't done any programming since my second semester of college, but let me see if I can dig up any of my old notes. I'm pretty sure I can do it from memory, but I wouldn't have the ability to test it until I went to school tomorrow.

Edited at Wed Oct 27, 2010 11:48:16 PM

Michael: Jodie, how's my schedule look for today?
Jodie: You've got a conference and dinner party at the Japanese Embassy regarding wildlife protection.
Michael: Oh, yeah...sorry, but I'll have to cancel that. I'm heading out to save America!

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Aron Schatz

2014: Year of change. Joined: August 3, 2001 Status: Offline Posts: 10753 Rep:

(No Title)

Thu Oct 28, 2010 8:35:39 AM #138331 Perm Link

In response to stinger608 #138322

try/catch blocks are for exceptions. You could do type checking for this assignment and Javascript is a loosely typed language.

What code have you got so far?

2014 is going to be a good year. More content, more streamlining. Be a part of history!

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stinger608

Joined: December 5, 2008 Status: Offline Posts: 169 Rep:

(No Title)

Thu Oct 28, 2010 6:55:12 PM #138351 Perm Link

So far, this is what I have.

Quote
var x=prompt("Enter a number between 0 and 10:","");
try
{
if(x>10)
{
throw "Err1";
}
else if(x<0)
{
throw "Err2";
}
else if(isNaN(x))
{
throw "Err3";
}
}
catch(er)
{
if(er=="Err1")
{
alert("Error! The value is too high");
}
if(er=="Err2")
{
alert("Error! The value is too low");
}
if(er=="Err3")
{
alert("Error! The value is not a number");
}

Does it look okay Aron?

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Tornado

Retro Grade Joined: August 16, 2003 Status: Offline Posts: 2958 Rep:

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Thu Oct 28, 2010 8:38:26 PM #138476 Perm Link

Have you tried compiling and testing it? Just looking at it I can see something that I would do differently, but I'm not sure if the way you have done it is actually wrong.

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stinger608

Joined: December 5, 2008 Status: Offline Posts: 169 Rep:

(No Title)

Thu Oct 28, 2010 9:15:06 PM #138478 Perm Link

In response to Tornado #138476

Said By Tornado
Have you tried compiling and testing it? Just looking at it I can see something that I would do differently, but I'm not sure if the way you have done it is actually wrong.

Share the suggestion Tornado. Please, this is very new too me, and I am having somewhat of a tough time with this language.......Jeez, not even sure why to be honest. Maybe I have gotten too used to HTML/CSS, Joomla, and WordPress. I would really like to understand this better, as it really enhances web sites, and is of course executed on the users end, taking a large burden off the server end.

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Aron Schatz

2014: Year of change. Joined: August 3, 2001 Status: Offline Posts: 10753 Rep:

(No Title)

Thu Oct 28, 2010 11:09:23 PM #138487 Perm Link

I'll try it out when I get back.

You learn something when you do web programming... never trust the client... EVER. Javascript is all well and good to handle certain ease of use (on the client), but all true functionality comes from the backend.

Regardless of how much validation you put into Javascript, you always do server side checks.

I still don't know why he wants you to use try/catch for this. I mean, exceptions are nice for stuff, but not this.

I'll give you an example of when to use exceptions. In a strong typed language (C++), you can use exceptions to give status of a function even if the function returns an integer. You could throw exceptions for improper inputs and other such stuff. That's when you do try{function();}catch(e){echo "ERROR!".e->errorText;} (Pseudo code).

Edited at Thu Oct 28, 2010 11:12:23 PM

2014 is going to be a good year. More content, more streamlining. Be a part of history!

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