conditional display of html element forms

Question

Well, after a one hour introduction to javascript, I ve come up with the following code. It did what I wanted alright, but then I wanted something else and it wont work.

I wanted that upon clicking on a button, a certain field would hide and on clicking on another yes, another one would hide too, BUT, of course, it had to make the other show, otherwise we would end up with nothing and the purpose was to present different fields depending on what the user clicked (on a radio button) So in a childish way I made my code and it worked. But then it came to me that I wanted first to have boths fields hidden instead of both fields shown, and here is the issue. I added a 0 value to the parameter of the function "telling it" that when x = 0, then visibility = hidden. But it wont listen to me!, So, the part of the code when it says x = 1 and 2 works, the one about 0, does not.

It is such a simple code that can make someone smile, but heck, it was clean and it worked. Does anyone know how to have the fields hidden before clicking on the buttons ?

Thanks a lot I remove some tags of the HTML

<html>
    <head>
        <script language="javascript">
            var x = 0;

            function hola(x) {
                if(x == 0) {
                    document.getElementById("cont1").style.visibility="hidden";
                    document.getElementById("cont2").style.visibility="hidden";
                }

                if(x == 1) {
                    document.getElementById("cont1").style.visibility="visible";
                    document.getElementById("cont2").style.visibility="hidden"; 
                }

                if(x == 2)  {
                    document.getElementById("cont1").style.visibility="hidden";
                    document.getElementById("cont2").style.visibility="visible"; 
                }
            }
        </script>
    </head>

    <body>
        <input type="button" onclick="hola(1)" value="hidefield2" id="boton1">
        <div id="cont1">
            <input type="text">
        </div>

        <input type="button" onclick="hola(2)" value="hidefield1" id="boton2">

        <div id="cont2">
            <input type="text">
        </div>
    </body>
<html>

Don't you think you should actually **call** the function with 0 as a parameter at some point? — Pointy, Oct 18 '10 at 17:09
Hello,thank you for taking the time to glance at my question. As per your comment, I think I have done that right at the start, I have put x = 0, but now that you say it, I am coming to think that that variable has no power to cross the line of the start of the function, that is, the function may be unaware of the assigment of 0 to x lines above. Therefore, if the default is naturally, visibility visible, that is why and since there was no further assigment then it stays. Then the explanation to the behaviour must probably that the X value = 0 declared prior to the function is not global. — Alvaro, Oct 19 '10 at 10:27

score 20 · Accepted Answer · edited May 27 '20 at 00:49

20

What worked:

You had two buttons, both visible in the beginning. And on click of one button, you hid a div, and made another visible.

Now you need a situation when the divs should be hidden in the beginning, and then show when you click a button.

By default, for all elements where a explicit visibility attribute is not given, visibility is considered to be visible.

To make the button invisible, you need to add visibility:hidden to the button.

You can do it two ways:

In the code for the divs, make then "invisible by default" by adding style='visibility:hidden'.

Add another javascript function that is called on load of the page, and makes both the divs invisible:

function hideBoth()  {  
   document.getElementById("cont1").style.visibility="hidden";  
   document.getElementById("cont2").style.visibility="hidden";   
}

Call it on load of your page: <body onload='hideBoth()'>

edited May 27 '20 at 00:49

jvarela

3,744
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answered Oct 18 '10 at 17:26

Nivas

18,126
4
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2

Thank you to both commenters: My conclusions after having worked with your proposals are: 1) I think the reason of the problem that the assigment of x = 0 would not work despite clearly existing a call to that is that the X was placed outside above before the beginning of the function. 2) If I hardcoded inline the visibility hidden in the html tag, although it did hide it, it would not show upon clicking on the buttons. 3) Finally, the onload call to the function from the body and the adding of the hideboth function did the trick. Thank you very much. Alvaro – Alvaro Oct 19 '10 at 10:37
1

Alvaro, just as you said for Problem #2, I tried both methods that Nivas said; the divs did not show on the click of the assigned button. Is there any fix? – WarpPrime May 27 '20 at 00:34

score 6 · Answer 2 · answered Oct 18 '10 at 17:08

This line:

document.getElementById("cont1").style.visibility="hidden";

Adds this:

style="visibility: hidden;"

to this:

<div id="cont1">

to make it look like this:

<div id="cont1" style="visibility: hidden;">

You can do this yourself, just by adding that attribute to your html tag.

Oh yeah, and this:

<div id="cont1">

is the same as this:

<div id="cont1" style="visibility: visible;">

score 1 · Answer 3 · answered Nov 12 '18 at 00:13

You can use jquery to also do this! Here is an example which basically takes the input of your CSS and makes it visible or not:

function checkPrerequisites() {
  // The 4th line makes objects visible in the for loop.
  // Determines if pre-requisites are met and if so - makes div draggable
  // for new courses 

  for (var i = 0; i < courselist.length; i++) {
    if (prerequisitesMet(i)) {
      $('#' + i.toString()).css("background-color", "lightgreen");
      $('#' + i.toString()).css("visibility", "visible");
      $('#' + i.toString()).draggable();
    }
  }
}

conditional display of html element forms

3 Answers3

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