Ask HN for help - JavaScript newbie with a problem. | Hacker News Reader

Ask HN for help - JavaScript newbie with a problem.

solipsys.co.uk

4 pointsColinWright12 comments

hiya Colin. It's been a while. Anyhow, the problem is in the 'type' of your script element:

  - <script type="javascript">
  + <script type="text/javascript">

Hiya - yes, and I owe you an email, I'm getting to it.

Anyway, file changed, but that doesn't seem to have fixed it. Any other suggestions?

jcr was partly right -- that change does need to be made -- but you also have to change the way that you reference the form element. You're using a very old (Netscape 4.0-era I think) way of referencing form elements in the DOM that apparently isn't supported anymore.

Add an id="results" attribute to the text box, then change the line in your display() function to this:

    document.getElementById('results').value = "test"

That works for me.

That looks like it works for me to - will upload now ...

Edit: Works on the server too. Thanks.

Any idea when this changed, and how I could've searched for this? Suppose someone took a JavaScript course back in pre-Netscape 4.0 - how would they come up-to-date?

As an algorithms person I find it completely baffling trying to learn, search, and investigate this stuff. It feels completely impenetrable. I have a PhD in Pure Math, and this makes me feel really thick.

Just a quick note of caution: id attributes are supposed to be unique to the entire document, so keep an eye out for that. document.getElementById() is the simplest way to target document elements that's supported by all browsers.

thanks thaumaturgy. I took my typical "make the problem simple" approach and replaced the function contents with:

  function displayx() {
    alert("Hello Nurse!");
  }

By the name change you can see my first guess was the name 'display()' might be causing the problem.

As for Colin's question about for searching for this kind of stuff, it helps to make the problem smaller and more isolated ("bifurcation" is the more typical/pedantic way to say it). In this case you could search on the very first step, the [onclick], find a working example, and see if you can get the example to run properly.

  <button onclick="alert('Hello Nurse!');">Click Me</button>

If it doesn't work, then you probably have a script blocker or popup blocker problem... or in my typical case, I've mistyped something important. ;)

From there, find a simple example of calling a function from onclick, and see if you it to run properly. If it works, then compare your code to the example. If the simple example doesn't work, then you might have a bad example, or you mistyped something, or there might be something odd in your browser config, or you've just found a bug in your browser, or ... --keep trying to simplify and isolate the problem.

The trouble with javascript searching and finding examples is finding bad examples. They're everywhere. The volume of bad JS code on the web is just staggering, but the worst parts are ancient, outdated and broken code still hanging around, and the existence of countless hacks to get around browser bugs/differences. The hacks can often look like horridly bad code, but sadly, they exist for a reason and they are seldom explained.

I'm not honestly sure when support for it was dropped; I know it fell out of favor at least 7 or 8 years ago. I can't quickly find a reference on the web to when support for legacy DOM was dropped, either.

For me, the third result for "javascript element value" is http://stackoverflow.com/questions/1988614/how-to-get-hidden...; the top result is a post full of techniques that work, but aren't what I'd use.

How you'd get up to date depends a little on how far you want to go with Javascript. If you just want to be able to do basic stuff and then get on with your work, probably your best bet is to use jQuery and start with their tutorials (http://docs.jquery.com/Tutorials:Getting_Started_with_jQuery). jQuery does a nice job of abstracting away many of the annoying things about the DOM and the various browser quirks associated with it.

If you wanted to really delve in to Javascript, I'm not really sure what to recommend. You would be throwing out most of the Netscape 4.0 way of doing things, and you'd eventually want to learn things like closures and Javascript's occasionally-annoying "everything is a global variable by default" and so on. One of the revered volumes would probably be best I guess: http://stackoverflow.com/questions/74884/good-javascript-boo...

I hear you on your frustration with it. Getting used to using the web inspector in Chrome or Firebug in Firefox helps, but error messages can be unhelpful, and you can find yourself swimming through lots of outdated (or incorrect, or even just "that's not how most people do things") blog posts when looking for answers. It's not quite like the good ol' days where you could drop in to a debugger and see the entire environment state and step through your code and so on. The mix of html and css and javascript also makes for this horrifically broad field of knowledge, most of which isn't really derivative, so it becomes a matter of trial-and-error and memorization.

That's a really, really useful reply. Thank you.

I don't get it. Why is this on HN?

Because not every hacker is a web developer. I, for example, am a self-confessed non-web developer. I program big iron and embedded systems in a safety critical context. I'm not scraping database for information and arranging it on the screen nicely for people to make purchases, I'm helping to stop oil tankers from crashing into nuclear submarines.

But occasionally I, and others, stray from our core competencies and either choose to or have to deal with things with which they are unfamiliar. In those cases it's nice to have a community to turn to consisting of people who do have expertise and experience in the unfamiliar area.

If it's not too often, and if it's obvious that people have made a genuine attempt to sort things out for themselves, and if the question is distilled to its essence, it's possible that more than one person can learn from the resulting thread.

And many times I've answered people's questions about math, or algorithms, and it's nice to get something back. So thank you to those who replied - it's pretty much sorted now, and I've learned something.

If you spend your days preventing the next global ecological or thermonuclear disaster and looking down your nose at those who do something like sell a product, I find it hard to believe that you have a hard time figuring out something like this without reaching out to the community in this manner, but that is another issue I'm not interested in. What I was asking about is the fact that I have been reading HN for about a year now and I've never seen a "story" like this come into my news feed. I was wondering why one suddenly popped.

I don't look down my nose at people "who do something like sell a product" - I have great respect for their skills, and for what they do. I, too, sell products and provide services, I just do it in a different context, albeit still computer based. Business-wise the activities have a lot in common. I'm trying to point out that the skills required in scraping databases and arranging things on screens is not what I do, and I find it hard. If nothing else it's an acknowledgement that people who do web development are skills I don't have.

    I find it hard to believe that you have a hard time
    figuring out something like this without reaching out
    to the community in this manner.

And I have a hard time believing that people struggle with some of the elementary math I see questions about, but I generally assume that they have other skills, and that this stuff is hard for them, so that's why I do what I can to help when I get the opportunity. Different people have different skills, different training, different experience and different talents.

    What I was asking about is the fact that I have been
    reading HN for about a year now and I've never seen
    a "story" like this come into my news feed. I was
    wondering why one suddenly popped.

Well, I've been reading HN for about 5 years now, and I've seen them before. Not often, and usually they are fleeting because the answers come quickly and efficiently, so the item never makes it to the Front Page. It doesn't have to.

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