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Storing a variable from an html document to display it in another

On the first page, the user is asked to select a name from a list (select/option tags) and click the "edit" button. User's choice is stored using the "option" variable and we redirect him/her to the next page.
When the body of the next page loads, it triggers the second function, which displays the option made previously as the main header of the page.
The problem is that, although onEdit() runs, displayOption() displays the variable as the empty string (as declared above the functions).
Why doesn't the second function "see" the alteration?
var option = "";
//"edit" button (onclick)
function onEdit() {
var selector = document.getElementById("selector");
option = selector.options[selector.selectedIndex].value;
window.location.href = "nextPage.html";
return false;
}
//"nextPage.html" body (onload)
function displayOption() {
var header = document.getElementById("header-main");
header.innerHTML = option;
}

Use local storage for that, it is easy to use and in this case highly appropriate.
See mdn docs
Example
on first page simply declare
localStorage.setItem('option', 'selectedOption');
on the second page get the var
var option = localStorage.getItem('option');
EDIT
as wendelin commented it is even more appropriate to use session storage, because it remove itself automatically.

The reason this doesn't work is that when nextPage.html loads, the entire script is re-evaluated, and option is now back to its default value of "".
You'll need another solution to persist the user's choice across refreshes. One of the more common approaches to something like this is to set the value as a query string parameter that can be read from within displayOption.

How to use the value of <div id =last_relay1></div> for create a loop condition in PHP?

I have a JS file that goes to my database and return the value,
The only values that can exist are 0 and 1.
After this I go to an PHP file I invoke this value however I want create a if condition loop to analyze the value of this div for display an image depending of the value.
For example:
if (<div id="last_relay1"></div> = 0) then display IMAGE A
else
if (<div id="last_relay1"></div> = 1) then display IMAGE B
My difficulty is to use the value of as a PHP variable.
//Script to load the value of the current relay
$(document).ready(function(){
setInterval(function(){
$("#last_relay1").load('last_update.php #RELAY1_STATUS_last_update')
}, 1000);
});
//little code to display the value of LAST_RELAY1 for database.
//the values returned possibles are 0 and 1
<div id="last_relay1"></div>

You can use a callback function with .load() to check the text of the DIV after it has been loaded. Use .text() to get the contents of the DIV.
$("#last_relay1").load('last_update.php #RELAY1_STATUS_last_update', function() {
if ($this).text().trim() == "0") {
$("#image").prop("src", "imageA.png");
} else {
$("#image").prop("src", "imageB.png");
}
});

I think what you are looking to do is to send data from the web page (generated by JavaScript) to PHP to decide which image to serve.
The way you framed the question won't help you find a solution (http://xyproblem.info/).
Instead, you will need to either:
preload both image A and image b, and display the one you want in javascript by unhiding it.
Dynamically load the image using PHP by making an XHR request that returns the correct image.

I solved it. I follow the tip provided by Barmar.
I used the following code...
var value = $("#last_relay1").load('last_update.php #RELAY1_STATUS_last_update', function() {
var value_to_test = value.text();
if(value_to_test == 1){
$("#last_relay1").empty();
$('<img src="img/ON.png">').appendTo("#last_relay1"); }
else {
$('<img src="img/OFF.png">').appendTo("#last_relay1");
}
});

setting a variable in javascript to be used in another form

I have form with a Grid (telerik), i think the technology behind it doesnt matter. I let user click on a row in the grid. During the click I extract a value from the Grid with Javascript, like so:
function RadDrillDoubleClick(sender, eventArgs) {
var Code = eventArgs.getDataKeyValue("Status");
if (Code == "In Progress" || Code == "")
{
location.href = "Main1.aspx?mode=edit&DID=" + eventArgs.getDataKeyValue("D_ID");
}
else {
location.href = "Main1.aspx?mode=view&DID=" + eventArgs.getDataKeyValue("D_ID");
}
}
After user has clicked the grid, I call this JS function and send them to correct .aspx page with either VIEW or EDIT mode dependent directly on the Code.
What I'm trying to do is once I get to the Main1.aspx page, I want to be able to continue to hold the CODE value, because when users performs a certain action, I'll need to call a javascript function and use the actual CODE to determine what the user will be able to do.....
var Code = eventArgs.getDataKeyValue("Status");
is there any way I can somehow create like a GLOBAL Variable called
CodeValue
that I can pass around to another form without doing it in the URL?

When the browser navigates to a page, all current JavaScript is unloaded from the browser. This means any functions/variables, etc. will not be accessible on the new page unless you've persisted the value in some way.
Common ways of persisting the value include:
Add it to the query string of the URL the user is navigating to
Save the value to a cookie
Save the value to local/session storage
For your scenario, #1 is probably your best bet (keep in mind the user can have multiple browsers/tabs open to your site).

One way to get the value from URL is like this: on the page Main1.aspx, you add to your JavaScript a function that will run after page loads and that will get what it needs from the current URL
var globalValue; // variable that will receive the value from URL
window.onload = function() {
var thisURL = window.location.href;
globalValue = url.split("?").pop();
// this will store in globalValue everything that comes after the last "?"
// example: if the url is www.site.com/text?value, it will store string "value" to globalValue
};

Can ajax be used for faceting/sorting?

I created a select from with popularity,high_to_low and low_to_high as options. I want the page to respond to these options dynamically using the ajax code
var http_option = createRequestObject();
function verifyRequest()
{
var option = document.getElementById("option").value;
if ( option )
{
var url = 'respond.pl?option='+option;
http_option.open('get', url );
http_option.onreadystatechange = handleResponse;
http_option.send(null);
}
}
function handleResponse()
{
if(http_option.readyState == 4 && http_option.status == 200)
{
var response = http_option.responseText; // Text returned FROM perl script
if(response) { // UPDATE ajaxTest content
document.getElementById("id_id").innerHTML = response;
}
}
If the value of the option is 1, images are displayed as stored in DB.
If the option is 2, images are to be displayed in descending order and
If the option is 3, images are to be displayed in ascending order
The respond.pl contain appropriate code for this sorting according to options and display images in a specified div tag.
The problem is that the page responds to the options only once and the next time on changing the option, the value of options shows "on" and not the numerals 1,2,3
I need this not only to sort images but also for faceting. If this is not the right option suggest the appropriate methods used for it.

It looks like your server-side program is returning HTML. And I think that's probably a mistake in this situation. I suggest returning JSON instead. Then, you can create an onChange event handler for your selector which simply re-orders the display. There are almost certainly a number of jQuery plugins that do this without you needing to write very much code.

Submitting form/getting HTML with JavaScript without iframe?

Context:
I work a student job transcribing paper reports in a webapp. It's old and we unfortunately can't change the source nor directly run a DB query.
It only checks if the unique ID exists once you submit the entire form, and you can't submit it unless it's entirely filled. Needless to say, it's a huge waste of time as you often transcribe the whole thing only to realise it's a duplicate.
Objective:
I made the userscript below that launches a search the search on the onblur of the unique ID's input(noReferenceDeclarant), checks if there are any matches (rows) and returns accordingly. Runs with Greasemonkey. The search form is in another page on the same domain. The search form does not take any URL arguments.
Can this be done without using an iframe (AJAX perhaps?)
This is a tool for my own productivity & to learn JS at the same time. As I'm still very much a beginner, any tips to make that code cleaner are welcome.
//Adding function to input's blur event
$(document).on ("blur", "#noReferenceDeclarant", isRefNumberExists);
//Vars
var noReferenceDeclarant = '';
var loadCode = 0;
var $searchForm;
//Fonctions
function isRefNumberExists ()
{
noReferenceDeclarant = $('#noReferenceDeclarant').val();
loadCode = 0;
//Make sure there's data in the input before proceeding
if (noReferenceDeclarant)
{
//Build search iframe
$searchForm = $('<iframe />', {
name: 'searchWindow',
src: 'rechercherGriIntranet.do?methode=presenterRechercher',
id: 'searchWindow',
width: 0,
height: 0
}).appendTo('body');
$searchForm.load(searchRefNumber);
}
}
function searchRefNumber()
{
var isExists = false;
//Check which "load" it is to avoid submit loops
if (loadCode === 0)
{
loadCode = 1;
//Filling search form with search term
$(this.contentDocument).find('#noReference').val(noReferenceDeclarant);
//Set search form preferences
$(this.contentDocument).find('#typeRapportAss').prop('checked', false);
$(this.contentDocument).find('#typeRapportAS').prop('checked', false);
$(this.contentDocument).find('#typeRapportSI').prop('checked', true);
//Submit the form
$(this.contentDocument).find('form:first').submit();
}
else if (loadCode === 1)
{
loadCode = 2;
//See if there are any tr in the result table. If there are no results, there a thead but no tr.
var foundReports = $(this.contentDocument).find('.resultatRecherche tr').length;
if (foundReports > 0)
{
if (confirm('A report matching this ID already exists. Do you want to display it?'))
{
//Modal window loading the report in an iframe. Not done yet but that's fairly straightforward.
}
else
{
//Close and return to the form.
}
}
}
//Reset variables/clean ressources
delete $searchForm;
$('#dateRedactionRapport').focus();
}

On the whole I've seen far, far worse code.
Ajax could do it, but then you'd just have to put the AJAX response into the DOM (as an iframe, most likely).
In this instance, I'd keep the approach you have. I think it is the sanest.j
Without the full context, there may be a way to clean up the loadCode -- but what you have is pretty same and works. A lot of folks would call it a semaphore, but that is just an issue of terminology.
The only thing I"d really clean up is recommend not calling the jQuery object so often..
// Many folks recommend that jQuery variables be named $<something>
var $doc = $(this.contentDocument);
doc.find('#typeRapportAss').prop('checked', false);
$doc.find('#typeRapportAS').prop('checked', false);
$doc.find('#typeRapportSI').prop('checked', true);
If you wanted to play with jQuery data structures, you could make a 'config' object that looks like this:
var formValues = {
typeRapportAs: false,
typeRapportAS: false,
typeRapportSI: true
};
then iterate over that to (using for ... in with .hasOwnProperty).
Not NEEDED for this project, what you are doing is fine, but it might make a learning exercise.