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What is a FORM's equivalent to DOM's getNextSibling?

I have a form, as follows:
<FORM name="form1">
<TABLE onkeypress="focusNextFormElement(event)">
<TR>
<TD><INPUT name="SomeObscureName"></TD><TD>Some data</TD>
</TR>
<TR>
<TD><INPUT name="ThisName"><span>Here's some obscure text.</span></TD><TD>Some data</TD>
</TR>
<TR>
<TD><INPUT name="someNameIdontKnow"></TD><TD>Some data</TD>
</TR>
</TABLE>
</FORM>
Is there a better, more efficient way to write this function? (Of course, this is a simplified example)
function focusNextFormElement(ev){
var el = ev.target;
var f = el.form;
var xx = f.elements.length - 1;
for(var x = 0; x < xx; x++){
if(f.elements[x] === el){
f.elements[x+1].focus();
}
}
}
There may be thousands of elements on this form, and I don't see it as particularly efficient to loop through them all each time the function runs.
Also, I could arbitrarily select an input with my mouse, so a tracking array may not be of much use.
I have no control of the generation of the page, as it's a greasemonkey script to help with automation of another page.
EDIT
Thanks to #Trincot and, from a broader point of view, #Oriol, the answer is found.
function nextFormSibling(el){
var elems = el.form.elements;
var idx = [].indexOf.call(elems, el);
return elems[idx+1] || el;
}
function previousFormSibling(el){
var elems = el.form.elements;
var idx = [].indexOf.call(elems, el);
return elems[idx-1] || el;
}

You could get the element's index calling indexOf() on the form's elements collection. Although this collection is not a native JavaScript array, you can use indexOf.call like this:
function nextFormElement(el) {
var f = el.form;
if (f) return f.elements[1+[].indexOf.call(f.elements, el)];
}
Here is a demo snippet using this function to move focus to the next element when a form element is clicked. This is obviously quite useless, but it shows that it works:
function nextFormElement(el) {
var f = el.form;
if (f) return f.elements[1+[].indexOf.call(f.elements, el)];
}
function focusNextFormElement(ev){
var el = nextFormElement(ev.target);
if (el) el.focus();
}
document.querySelector('form').onclick = focusNextFormElement;
<FORM name="form1">
<TABLE onkeypress="focusNextFormElement(event)">
<TR>
<TD><INPUT name="SomeObscureName"></TD><TD>Some data</TD>
</TR>
<TR>
<TD><INPUT name="ThisName"><span>Here's some obscure text.</span></TD><TD>Some data</TD>
</TR>
<TR>
<TD><INPUT name="someNameIdontKnow"></TD><TD>Some data</TD>
</TR>
</TABLE>
</FORM>

Basically, no, without knowing the strusture of the DOM a priory, you need the index of the element in the elements collection in order to access the next one. And iterating it seems the only way, but consider using indexOf instead of doing it manually.
However, if you want to access the next element multiple times, you can do it only once and cache the result:
var nextFormElement = (function() {
var cache = new WeakMap();
return function(el) {
if(!cache.has(el)) {
var els = el.form.elements,
idx = [].indexOf.call(els, el);
cache.set(el, els[idx+1] || null);
}
return cache.get(el);
};
})();
If ES6 is not supported you can use a plain object instead of a weakmap, where the values are the next elements, and the keys are some identifiers which you can store in the elements as data-* attributes.
Then, use it like
var next = nextFormElement(event.target);
if(next) next.focus();
var nextFormElement = (function() {
var cache = new WeakMap();
return function(el) {
if(!cache.has(el)) {
var els = el.form.elements,
idx = [].indexOf.call(els, el);
cache.set(el, els[idx+1] || null);
}
return cache.get(el);
};
})();
document.forms.form1.addEventListener('keypress', function(event) {
var next = nextFormElement(event.target);
if(next) next.focus();
});
<form name="form1">
<div>
<input name="SomeObscureName" />
<span>Some data</span>
</div>
<div>
<input name="ThisName" />
<span>Here's some obscure text.</span>
<span>Some data</span>
</div>
<div>
<input name="someNameIdontKnow" />
<span>Some data</span>
</div>
</form>
That said, this code is completely obtrusive, and I don't recommend it. If the user wants to focus the next text focusable field, he can use the tab key. If he doesn't want to change focus and you do it for him, it will be so annoying.

Assuming that the HTML strictily adeheres to your example you can try :
function focusNextFormElement (ev) {
// First find the tr element of this input...
var tr = ev.target.parentNode.parentNode; // find the tr node
// Advance to the next table row ...
tr = tr.nextElementSibling
// Then focus the input element in that row...
tr.querySelector ('input').focus ();
}

Could you elaborate as what are you planning to achieve? Do you want to keep shifting your Input Focus to Input Elements? If so, it's better you should use the 'tabindex' attribute.
Rer: http://www.wufoo.com/html5/attributes/27-tabindex.html
If not, then would like to know more about the problem.
Note: Your 'onkeypress' on 'TABLE' element has more problem because, for every key pressed in the input field, it immediately switches to next input field.

Check if all input/select fields of a table row have values

There is a table with some input and select fields in a row. I want to check if all input and select fields of an row have a value. This is how I would think to do that, but do I have to use closest and find? I think this is not optimal.
HTML
<table>
<tr>
<td><select><option></option><option>Select anything</option></td>
<td><input type="text" name="field1"></td>
<td><input type="text" name="field2"></td>
</tr>
<tr>
<td><select><option></option><option>Select something</option></td>
<td><input type="text" name="field3"></td>
<td><input type="text" name="field4"></td>
</tr>
</table>
JS
'change #table input, change #table select': function(event) {
var $this = $(event.currentTarget),
$row = $this.closest('tr'),
$elements = $row.find('input, select');
var empty = false;
$elements.each(function(index) {
if (!$(this).val()) empty = true;
});
if (empty)
console.log('some value is missing')
else {
console.log('valide');
// do something with values
}
}

There are really two questions here:
Most optimal method to select all inputs in a table row
Ensure all the inputs have a value
For the first question there is a subliminal side to that. Ensure that it IS an input and then select it within the context of the current row of the changed input.
First off, jQuery uses the Sizzle (https://sizzlejs.com/) engine under the covers for selection. One thing to be aware of is the "right to left" processing of the selector string by that engine.
Thus the most optimal selection is somewhat browser specific but the fastest way to select is an ID followed in modern browsers by a class. Some older browsers do not select by class as well but let's leave that for your research.
Selection: Bad way to do stuff
So given that, let's look at a complex selector that you might use:
'div.mycontainer div.mytablecontainer>table#mytable.mytableclass tr td select, div.mycontainer div.mytablecontainer>table#mytable.mytableclass tr td input'
First off DO NOT USE THAT. Now to explore why not: Remember we talked about the "right to left" selector processing? For discussion let us narrow down out selector to the last part:
"div.mycontainer div.mytablecontainer>table#mytable.mytableclass tr td input"
What this does then in starting on the right:
"find all the inputs in the DOM",
use that list of those inputs, "find all the inputs in a td element
use those td elements, find all those in a tr
find all those tr in a .mytableclass element
find all those in an element with an id of mytable (remember this ID MUST be unique)
Now keep going, find that single element id that is a table element
That is an immediate child of an element with classmytablecontainer
That is a DIV element div
That is a child of an element with class mycontainer
That is a DIV element div
Whew that's a lot of work there. BUT we are NOT DONE! We have to do the same thing for the OTHER selector in there.
Selection: Better way to do stuff
NOW let's do this better; first off let's leverage the modern browser class selector by adding a class to all our "scoped" inputs - things we want to check for entry.
<input class="myinput" />
It does really need a type="" attribute but ignore that for now. Let's use that.
$('#mytable').find('.myinput');
What this does is:
Select the element with ID of 'mytable' which is the FASTEST selector in all browsers; we have already eliminated those 47 other tables in our DOM.
Find all the elements with a class of class="myinput"; within that table; in modern browsers this is also very fast
DONE. WOW! that was SO much less work.
Side note on the .find() instead of "#mytable input"
Remember our right to left once again? Find all inputs in the DOM, then narrow to those inputs we found that are in that table NO STOP THAT right now.
Or (better likely) "#mytable .myinput"
SO our "rules" of selecting a group of elements are:
Use an ID to limit scope to some container if at all possible
Use the ID by itself NOT part of a more complex selector
FIND elements within that limited scope (by class if we can)
Use classes as modern browsers have great selection optimization on that.
When you start to put a space " " or ">" in a selector be smart, would a .find() or .children() be better? In a small DOM perhaps maintenance might be easier, but also which is easier to understand in 4 years?
Second question: not specific but still there
You cannot simply globally use !$(this).val() for inputs.
For a check box that is invalid. What about radio buttons? What about that <input type="button" > someone adds to the row later? UGH.
SO simply add a class to all "inputs" you DO wish to validate and select by those:
<input type="text" class="validateMe" />
<select class="validateMe" >...
Side note you MIGHT want to sniff the TYPE of the input and validate based upon that: How to get input type using jquery?
EDIT: Keep in mind your validation input MIGHT have a "true/false" value so then this might fail: !$(this).val() (radio buttons, checkbox come to mind here)
Some code and markup:
<table id="mytable">
<tr>
<td>
<select class="myinput">
<option></option>
<option>Select anything</option>
</select>
</td>
<td>
<input class="myinput" type="text" name="field1" />
</td>
<td>
<input class="myinput" type="text" name="field2" />
</td>
</tr>
<tr>
<td>
<select class="myinput">
<option></option>
<option>Select something</option>
</select>
</td>
<td>
<input class="myinput" type="text" name="field3" />
</td>
<td>
<input class="myinput" type="text" name="field4" />
</td>
</tr>
</table>
<div id="results">
</div>
probably NOT want a global (namespace the "selectors")
var selectors = '.myinput';
$('#mytable').on('change', selectors, function(event) {
var $this = $(event.currentTarget),
$row = $this.closest('tr'),
$elements = $row.find(selectors);
var $filledElements = $elements.filter(function(index) {
return $(this).val() || this.checked;
});
var hasEmpty = $filledElements.length !== $elements.length
var rowIndex = $row.index();
$('#results').append("Row:" + rowIndex + " has " + $filledElements.length + ' of ' + $elements.length + ' and shows ' + hasEmpty + '<br />');
if (hasEmpty)
console.log('some value is missing');
else {
console.log('valide');
// do something with values
}
});
AND something to play with: https://jsfiddle.net/MarkSchultheiss/fqadx7c0/

If you're only selecting on particular element with knowing which parent to select with, you should try using .filter() to filter out only element that did't have a value like following :
$('button').click(function() {
var h = $('table :input').filter(function() {
return $(this).val() == "" && $(this);
}).length;
alert(h);
});
DEMO

I did this plunk
https://plnkr.co/edit/q3iXSbvVWEQdLSR57nEi
$(document).ready(function() {
$('button').click(function() {
var table = $('table');
var rows = table.find('tr');
var error = 0;
for (i = 0; i < rows.length; i++) {
var cell = rows.eq(i).find('td');
for (a = 0; a < cell.length; a++) {
var input = cell.eq(a).find(':input');
if (input.val() === "") {
input.css("border", "solid 1px red");
error++;
} else {
input.css("border", "solid 1px rgb(169, 169, 169)");
}
}
}
if (error > 0){
alert('Errors in the form!')
return false;
} else {
alert('Form Ok!')
return true;
}
})
})
Simple Jquery validation, searching all the inputs (including selects), if it's null, increment the error counter and change class. If the error counter is > 0, alert error and return false;
Maybe isn't the best solution, but it sure can help get started.

javascript - addEventListener with an array of input

I need to use addEventListener for automatically updating the values typed into different input text (actually 4 input tags)
Here's the HTML code :
<td class="col-md-4">
<label for="lab1"><b>$\mathbf{M_{1}}$</b></label>
<input type="text" class="form-control input-sm" id="lab1" />
</td>
<td class="col-md-4">
<label for="lab2"><b>$\mathbf{M_{2}}$</b></label>
<input type="text" class="form-control input-sm" id="lab2" />
</td>
<td class="col-md-4">
<label for="lab3"><b>$\mathbf{M_{3}}$</b></label>
<input type="text" class="form-control input-sm" id="lab3" />
</td>
</tr>
<tr>
<td class="col-md-4">
<label for="lab4"><b>$\mathbf{\Theta_{1}}$</b></label>
<input type="text" class="form-control input-sm" id="lab4" />
</td>
I would like to update values when they are modified, without having to click outside the input.
I tried to use the following addModifyEvent function in main :
function addModifyEvent() {
var inputList = document.querySelectorAll('input.form-control');
for (var i=0; i<inputList.length; i++)
{
inputList[i].addEventListener('input', function()
{
console.log(inputList[i].value); });
}
}
but it doesn't work ( I get TypeError: inputList[i] is undefined).
I don't know if I shoud better do :
inputList[i].addEventListener('inputList['+i+']',
or something closed instead of
inputList[i].addEventListener('input',
I want to add an eventlistener for each input tag.
Anyone could tell me the right syntax ?
Thanks

As you can see in example i printed 2 console one for your input and one for your i
So your problem is:
when in listener function you are trying to access
console.log(inputList[i].value); so at that time your i is 4 and your input array length is 0-3 and because of for loop i will
be incremented to 4 so you got undefined because inputList[4] is
not present in your array.
Working example:http://jsfiddle.net/kevalbhatt18/gqce9htx/
var input = document.querySelectorAll('input');
console.log(input)
for(var i=0;i<input.length;i++){
input[i].addEventListener('input', function()
{
console.log(input)
console.log(i)
console.log('input changed to: ', this.value);
});
}
debugg your error example:http://jsfiddle.net/kevalbhatt18/gqce9htx/2/

The context of the event handler is the input element the event is fired on. Replace the inputList[i] with this:
console.log(this.value);

A slightly modified version of your code that uses this.value works just fine:
function addModifyEvent() {
var inputList = document.querySelectorAll('input.form-control');
for (var i = 0; i < inputList.length; i++) {
inputList[i].addEventListener('input', function () {
console.log(this.value);
});
}
}
Demo: http://jsfiddle.net/jfriend00/9ny3wcxu/
You can't refer to inputList[i] inside the event handler because by the time the event handler is called (sometime later) the for loop has already finished running so i points past the end of the inputList HTMLCollection object.
You can solve the problem by just using this as a pointer to the object that caused the event and thus this.value is the value of the input field that has just been modified.

At the time the event fires,
console.log(inputList[i].value);
inputList[i] will not be valid as it was part of the for loop used to bind event listeners.
Use this to get the current element on which the event was fired,
console.log(this.value);
Full code
function addModifyEvent() {
var inputList = document.querySelectorAll('input.form-control');
for (var i = 0; i < inputList.length; i++) {
inputList[i].addEventListener('input', function () {
console.log(this.value);
});
}
}

You can use closures (if not familiar, please search it and read a bit). The code goes as below:
for (var i=0; i<inputList.length;i++)
{
(function(i){
inputList[i].addEventListener('input',function(){
console.log(inputList[i].value); });
}
})(i);
}
Basically the value of i remains intact within the function. This is required whenever you do something in a loop that is Async. The benefit being that you do not need to change the way you access values, except that you need to enclose them within a closure function. Hope this solves you issue without any changes in the way to want to access the array.

var inputElem = document.getElementsByTagName('input');
for(var i = 0; i < inputElem.length; i++) {
inputElem[i].addEventListener('click', function(){
alert(this.value);
}, false);
}

javascript id change onclick function

So I got a 3 x 3 table wich looks like this:
<table align=left width="896px" class="tableCategories">
<tr class="trCategories">
<td class="tdCategories"><input type="button" id="P11" onclick="clickE()" value="E" /></td>
<td class="tdCategories"><input type="button" id="P12" onclick="clickS()" value="S" /></td>
<td class="tdCategories"><input type="button" id="P13" onclick="clickB()" value="B" /></td>
....
I just want that if the user clicks on one of the nine boxes all of the boxes changes their background images and the box which was clicked changes itself to a back button which references to the first 9 images. Like a submenu getting opened if one of the boxes being clicked.
So I tried it in my way but it does not work very well. If I click on one of the boxes it triggers both actions which is connected via id. So my thought was to change the id to, but then I thought maybe there is a smarter way to do that. So I wrote my problem here :D
Edit:
The javascript part is looking like this for every of the functions:
function clickE()
{
document.getElementById("P11").value = "Zurück";
document.getElementById("P11").onclick = clickBack;
document.getElementById("P12").value = "Restaurant";
document.getElementById("P12").onclick =clickCategory("restaurant");
document.getElementById("P13").value = "Imbiss";
document.getElementById("P13").onclick =clickCategory("imbiss");
document.getElementById("P21").value = "Bäckerei";
document.getElementById("P21").onclick =clickCategory("baeckerei");
document.getElementById("P22").value = "Fast Food";
document.getElementById("P22").onclick =clickCategory("fast_food");
document.getElementById("P23").value = "Süßes";
document.getElementById("P23").onclick =clickCategory("suesses");
document.getElementById("P31").value = "Cafe";
document.getElementById("P31").onclick =clickCategory("cafe");
document.getElementById("P32").value = "Bar";
document.getElementById("P32").onclick =clickCategory("bar");
document.getElementById("P33").value = "Kneipe";
document.getElementById("P33").onclick =clickCategory("kneipe");
}
I try it first with the labels because I think it will work with images the same way.

Being unsure of the long term application, I may have a starting point. The initial script provided could get a bit unwieldy if you ever want to extend, so there is now a "defineElements" method that could be used to configure your elements. Please note that argument paramaters have been added to the onclick event in the html as well.
The "defineElements" function returns an associative array object (eg key/value pairs), with each key being named after the html element id. The value of each key is also an associative array that contains the element id (eid), label (lbl) and event (evnt).
Short story long... when you click a button, the label for each button is changed and the appropriate click handler is assigned. If you click the button labeled "Back", the default click handler is reassigned to all.
This would also be an excellent candidate for jQuery if that is available to you.
Hopefully this will get you moving in the right direction:
HTML
<table>
<tr class="trCategories">
<tr class="trCategories">
<td class="tdCategories"><input type="button" id="P11" onclick="clickE(this.id)" value="E" /></td>
<td class="tdCategories"><input type="button" id="P12" onclick="clickS(this.id)" value="S" /></td>
<td class="tdCategories"><input type="button" id="P13" onclick="clickB(this.id)" value="B" /></td>
</tr>
</table>
== And the Javascript
function clickE(id){
var elementDef = defineElements(id);
for(var key in elementDef){
var propObj = elementDef[key];
//console.log(propObj);
document.getElementById(propObj.eid).value = propObj.lbl;
if(id == undefined)
document.getElementById(propObj.eid).onclick = function(){ clickE(this.id);} //--reassign default event
else
document.getElementById(propObj.eid).onclick = propObj.evnt;
}
}
function defineElements(id){
var elementArr = ['P11','P12','P13']; //--add your element id's to this array to extend, and then add a case for each within switch below
var definitionObj = {};
for(var i = 0; i < elementArr.length; i++){
switch(elementArr[i].toUpperCase()){
case 'P11':
definitionObj[elementArr[i].toUpperCase()] = { eid:elementArr[i].toUpperCase(), lbl:'Zuruck', evnt: function(){ clickCategory.call(this, "whatever"); } };
break;
case 'P12':
definitionObj[elementArr[i].toUpperCase()] = { eid:elementArr[i].toUpperCase(), lbl:'Restaurant', evnt: function(){ clickCategory.call(this,"restaurant"); } };
break;
case 'P13':
definitionObj[elementArr[i].toUpperCase()] = { eid:elementArr[i].toUpperCase(), lbl:'Imbiss', evnt: function(){ clickCategory.call(this,"imbiss"); } };
break;
}
}
if(id != undefined){
definitionObj[id]['evnt'] = function(){ clickBack.call(this); } //--assign the clickback function to the selected element based on id paramater
definitionObj[id]['lbl'] = 'Back';
}
return definitionObj;
}
function clickCategory(cat){
alert(cat);
}
function clickBack(){
clickE();
}

Loop through form input fields with Javascript

Please help me out on this. I have Javascript like the following:
function calc() {
var table = document.getElementById(tableNum);
var rowCount = table.rows.length;
for (var i = 0; i < rowCount; i++) {
var totalNum[i] = document.formNum.txt1[i].value * document.formNum.txt2[i].value;
document.getElementById('totalCalc[' + i + ']').innerHTML = totalNum;
}
}
And HTML like this:
<table id="tableNum">
<form name="formNum" action="" id="formNum">
<tr>
<td><input type="text" name="txt1[]" onkeyup="calc()"/></td>
<td><input type="text" name="txt2[]" onkeyup="calc()"/></td>
<td><span id="totalCalc[]"></span></td>
</tr>
</form>
</table>
The number of input fields is unknown. No error, but totalCalc field is empty. Please tell me what I have done wrong. Thanks.
EDIT: I'm sorry, I forgot to mention both the input fields are in a table. Please check the edited code. Thanks.
EDIT: I'm actually working on a demo which the number of table row is defined by user, by clicking insert row button.
EDIT: Thanks Travis for the code. After a few changes, the code is working now. But only the first row is working. I'm thinking to get the length of the row and to use for loop for the text fields. <input type="text" name="txt1[<?php echo $rowLength;?>]" onkeyup="calc()"/> Does anyone have other ideas? Thanks.

The first thing seems wrong is
document.getElementById(tableNum);
should be
document.getElementById("tableNum");
Secondly,
var totalNum[i] =
should be
var totalNum =
Also, its not working, you can find it out quickly by debugging through firebug or chrome's integrated developer tool. Which will help you for syntax verification as well.

Here is what is going on.
HTML first
If you are going to reference these by indices, then use proper indices, like this
name="txt1[0]"
name="txt2[0]"
<span id="totalCalc[0]">
Javascript
document.getElementById(tableNum);
getElementsById expects a string, so this should be
document.getElementById("tableNum");
Since you are iterating, you only need one of these variables since it is immediately used (not a whole array):
var totalNum = instead of var totalNum[i]
When you access the form using dot notation, the brackets in the name messes that up, you need to do it like this:
document.formNum["txt1["+i+"]"].value instead of document.formNum.txt1[i].value
Vuala
When you make these minor changes, the code you used will actually produce proper results :) See this working demo: http://jsfiddle.net/69Kj7/ , also, here is a demo with 2 rows: http://jsfiddle.net/69Kj7/1/
For reference, this is the code in the demo:
html:
<table id="tableNum">
<form name="formNum" action="" id="formNum">
<tr>
<td><input type="text" name="txt1[0]" onkeyup="calc()"/></td>
<td><input type="text" name="txt2[0]" onkeyup="calc()"/></td>
<td><span id="totalCalc[0]"></span></td>
</tr>
</form>
</table>​
js:
function calc() {
var table = document.getElementById("tableNum");
var rowCount = table.rows.length;
for (var i = 0; i < rowCount; i++) {
var totalNum = document.formNum["txt1["+i+"]"].value * document.formNum["txt2["+i+"]"].value;
document.getElementById('totalCalc[' + i + ']').innerHTML = totalNum;
}
}​

if you wants to work with pure java script and here is the logical code
html
<form name="formNum" id="formNum" action="" >
<input type="text" name="foo[]" onkeyup="calc()" value="5"/>
<input type="text" name="foo[]" onkeyup="calc()" value="12"/>
<span id="totalCalc"></span>
</form>
​
js
var inputs = formNum["foo[]"];
var total = 1;
alert(inputs.length);
for (var i = 0; i < inputs.length; i++) {
total *= inputs[i].value;
}
alert(total);
working DEMO

I've figured out how to solve the problem. Just insert array after totalCalc, but not within totalCalc.
Thank you guys so much for helping me out :)