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A textbox will only be visible if it has some value to show from databse using JavaScript

I want to make a text box visible only if has some value from DB.
I have tried the following code but it doesn't work properly.
<input type="text" name="p_name" id="txt1" value="<%=class1.getName()%>" style="display:if(document.getElementById('txt1')!=''){document.getElementById('txt1').style.display='block';}else{document.getElementById('txt1').style.display='none';};">
Please help me to solve this problem using JavaScript and HTML.

You can not use Javascript in the style attribute of the input element. Instead, use javascript with a <script> tag to run it properly. All you have to do is to determine if the input is empty or not and hide it accordingly.
Two examples, with the same Javascript:
Input not empty:
document.addEventListener('DOMContentLoaded', _ => {
const txt1 = document.getElementById('txt1');
txt1.style.display = txt1.value && txt1.value !== '' ? 'block' : 'none';
});
<input type="text" name="p_name" id="txt1" value="<%=class1.getName()%>">
Input empty:
document.addEventListener('DOMContentLoaded', _ => {
const txt1 = document.getElementById('txt1');
txt1.style.display = txt1.value && txt1.value !== '' ? 'block' : 'none';
});
<input type="text" name="p_name" id="txt1">

You can write a script for it using the same conditions as you are currently using and hide the text box by
$('#txt1').hide()
Similarly use show() function to show the text box.

JQuery Not Triggering On Button.click

I've written some code that should check a textbox (ID tfa_1) to see if its empty or contains text, this should trigger on a next page button (wfpagenextID6) being clicked.
I've tried replacing my script with an alert("test.") and it dosent appear, so im assuming I have my trigger wrong but I cannot work out what I have done wrong!
My HTML that defines the textbox is below:
<input type="text" id="tfa_2685" name="tfa_2685" value="" placeholder="" title="Previous Surname (if applicable) " class="">
and the button is
<input value="Next Page" type="button" class="wfPageNextButton" wfpageindex_activate="7" id="wfPageNextId6" style="visibility: visible;">
Both of these are generated and I cannot change them!
My Script is:
<script>
$(document).ready(function(){
$('#wfPageNextId6').click(function(){
var inp.Val= $("#tfa_2685").val();
if (inp.val().length > 0) {
alert("Test.");
}
});
})
</script>

An identifier ( variable ) must not contains dots. ( see more details ECMAScript specification in section 7.6 Identifier Names and Identifiers)
the next variable declaration is wrong
var inp.Val= $("#tfa_2685").val();
to fix this
var inp = $("#tfa_2685");

if you want to assign value to inp variable, you should just do: var inp = $("#tfa_2685").val();
And then call to inp.val() just replace with inp, for inp is not jQuery object so it doesn't have val() method

You have syntax, try this:
$(document).ready(function(){
$('#wfPageNextId6').click(function(){
var inpVal= $("#tfa_2685").val();
if (inpVal.length > 0) {
alert("Test.");
}
});
});
https://jsfiddle.net/cua40s80/

Jquery: Combine multiple user inputs into one text area?

I'm trying to put together multiple user inputs and then combine them into one textarea after button click.
For example:
User1:Hey, I just met you
User2:And this is crazy
User3:But Here's my number so call me maybe
Combined Result:
Hey, I just met you, And this is crazy, But Here's my number so call me maybe
Here's my code the button click is currently not working but when I tried it before it did work so I was thinking I have some problem w/ my Jquery that triggers this unusual result:
HTML and Imports:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<input class="combine" id="input1" disabled="true"></input>
<input class="combine" id="input2" disabled="true"></input>
<input class="combine" id="input3" disabled="true"></input>
<input class="combine" id="input4" disabled="true"></input>
<input class="combine" id="input5" disabled="true"></input>
<input class="combine" id="input6" disabled="true"></input>
<input class="combine" id="Voltes5" disabled="true" size="45"></input>
<button id="setVal">Set</button>
Jquery
$(document).ready(function(){
$('#setVal').on('click',function(){
jQuery(function(){
var form = $('.combine');
form.each(function(){
$('.Voltes5').append($(this).text()+ ' ');
});
});
});
});
Update for sir Arun P Johny
User1: If theres a (no comma when combined)
User2: will
User3: there's a way
Combined Result:
If theres a will, there's a way

Try
$(document).ready(function () {
$('#setVal').on('click', function () {
var form = $('.combine').not('#Voltes5');
var vals = form.map(function () {
var value = $.trim(this.value)
return value ? value : undefined;
}).get();
$('#Voltes5').val(vals.join(', '))
});
});
Demo: Fiddle

Here's a one-liner for non-readability ;)
$('#setVal').click(function(){$('#Voltes5').val($('.combine').not('#Voltes5').map(function(){return $(this).val();}).get().join(''))});
Expanded:
$('#setVal').click(function(){
$('#Voltes5').val(
$('.combine')
.not('#Voltes5')
.map(
function(){
return $(this).val();
})
.get()
.join('')
);
});
Get fiddly with it: http://jsfiddle.net/ArtBIT/u57Zp/

Here is one way to do this:
$('#setVal').on('click', function () {
$(".combine[id^=input]").each(function () {
if(this.value) {
$("#Voltes5")[0].value += ' ' + this.value;
}
});
});

There are several different ways to do this..
I'd do it this way using an array:
$(document).ready(function () {
$('#setVal').on('click', function () {
//create an array for the values
var inpAry = [];
$('.combine').each(function () {
//add each value to the array
inpAry.push($(this).val+' ');
});
//set the final input val
$('#Voltes5').val(inpAry);
});
});
but you would need to remove the combine class from #setVal because that would be included in the .each.
This way it would also be possible to have the final box updated on keyup as I'm not just appending the values, the combined values are set each time.

$(document).ready(function(){
$('#setVal').on('click',function(){
var val='';
$('.combine').not('#Voltes5').each(function(){
val+=$(this).val();
});
$('#Voltes5').val(val);
});
});
.text() will give text of the element ,for input val u have to use .val()

So there's immediate big problem in the code, which is that you're referring to your Voltes5 element as a class, not an ID. The jQuery selector you want is:
#Voltes5
instead of:
.Voltes5
There are a few other things to think about too, though, for the sake of functionality and best practices. Firstly, the Voltes5 element also has class combine, meaning that the $('.combine').each() call will include this element. The outcome of this is that it will also append its current text to itself when the code is run (or, when the code is run with the above correction).
When grabbing the current entered text of an input element, a jQuery .val() call is what you want, not .text() - see this answer for some more discussion.
Another thing that could be noted is that you should really explicitly specify what sort of input these elements are; <input type="text"> is hugely preferable to <input>.
Finally, input is a void element (reading), meaning it shouldn't have any content between opening and closing tags. Ideally, you wouldn't even give a closing tag; either have just the opening tag, or self-close it:
<input>
<input />
HTH

replace $('.Voltes5').append($(this).text()+ ' ');
with
$('#Voltes5').append($(this).text()+ ' ');

How to clear a text field?

I want to place a cross button next to a text field, which, on clicking it, clears the value entered by the user. In other words, it empties the field. Please help..
And I also want to focus the field, but after some 2 or 3 seconds..

Like this:
$('#myButton').click( function () {
$('#myField').val('');
});
Or without jQuery
document.getElementById('myButton').onclick = function () {
document.getElementById('myField').value = '';
});

Try this,
$('#button').click(function(){
$('#inputBox').val('');
});

Have you tried anything at all? But this should do (edit after misread, see below):
$('#your_button').click(function() { $('#your_textbox').val(''); });

In Javascript:
document.getElementById('textField1').value = "";

Well, learn to break your tasks into smaller one and everything will become much easier. Here, for example, you have 2 tasks:
1) Place a "X" button near input. This is achieved by CSS and HTML. You HTML might look like:
Then you should align your image with you input
2) Actual erasing. In jQuery:
$("#x_button").click( function() {
$("#input_id").val( "" );
});
But this is real basics of web development, so you should really consider to read some kind of book on it.

You can do it with html5 value.
<input type="text" placeholder="Your text here">

Assuming your text field looks like this one :
<input type="text" id="myText"></input>
and your button looks like this one :
<input type="button" id="myButton"></input>
You just have to do this in javascript :
<script type="text/javascript">
var myButton = document.getElementById('myButton');
myButton.addEventListener("click", function () {
document.getElementById('myText').value = '';
}, false);
</script>
If you're using jQuery it's even easier :
<script type="text/javascript">
$('#myButton').click(function() {
$('#myText').val('');
});
</script>

here is a sample:
Html:
<input type="text" id="txtText" value="test value" />
<input type="button" id="btnClear" value="Clear" />
javascript:
$(document).ready(function () {
$("#btnClear").click(ClearText);
});
function ClearText() {
$("#txtText").val("");
}

can the name of a input tag be changed with javascript?

I want to know if its possible to change the name of the input tag with javascript or jquery, for example in this code :
<input type="radio" name="some_name" value="">
I want to change the some_name value when user select this radio button.
the reason what i want to do this is described here : How might I calculate the sum of radio button values using jQuery?

Simply elem.name = "some other name" or elem.setAttribute("name", "some other name") where elem is the element you want to alter.
And to do that on selection, use the onchange event:
<input type="radio" name="some_name" value="" onchange="if(this.selected) this.name='some other name'">
And to apply that behavior to every radio button with that name:
var inputElems = document.getElementsByTagName("input");
for (var i=inputElems.length-1; i>=0; --i) {
var elem = inputElems[i];
if ((elem.type || "").toLowerCase() == "radio" && elem.name == "some_name") {
elem.onchange = function() {
if (this.selected) {
this.name = "some other name";
}
};
}
}
But using jQuery for that is quite easier.

The jQuery way
$('input:radio[name="some_name"]').attr('name', 'new name');
Gumbo has the vanilla JavaScript way covered

Yes, you can change the name of any element with javascript. Keep in mind though that IE 6 and 7 have trouble with submitted forms where the input elements have been tinkered with in javascript (not sure if this exact case would be affected).
$('input:radio[name="some_name"]').attr('name', 'new_name');
Edit: To change it only when it is selected, here is the code for that:
$("input:radio[name='some_name']").click(function() {
if ($(this).attr('checked')) $("input:radio[name='some_name']").attr('name', 'new_name');
else $("input:radio[name='some_name']").attr('name', 'some_name');
});

Sure. If jQuery is your poison, this should do the trick:
$("input[name=some_name]").attr("name", "other_name");

I came up with this:
<input type="radio" name="some_name" value="" id="radios">
<script type="text/javascript" charset="utf-8">
$(document).ready(function()
{
$("#radios").click(function()
{
$(this).attr("name", "other_name");
});
});
</script>

Trying to change the name attribute of a radio button will cause strange, undesirable behavior in IE.
The best way to handle this is to replace the old radio button with a new one. This post may help you. If you are using jQuery, you can do it with the replaceWith function.
More information about changing name attributes in IE.