I have a JavaScript map that takes some coordinates from a django view/function when the template page first loads up like this:
<script type="text/javascript">
...
map.setCenter(new f.LatLng{{lat_long}}, 11);
...
</script>
I also have another function on the same views.py file handling an ajax request that does some calculations and returns new coordinates that supposed to update the same spot where {{lat_long}} tag is.
So in a way I should make the {{lat_long}} coming from the function when the page first loads up disappear and replace it with a new {{lat_long}} that's coming form the function handling the ajax request.
What would be the best way to go about this so both functions can update the same lat/long in the javascript code above? Real examples will be truly appreciated.
What Chris said is correct. You want to dynamically update the value from the server. Putting the code where you have it now just does it when the page is loaded, you need to use an AJAX request to keep asking the server for the latest value.
What you need to do is make another Django View that just returns the latitude and longitude, JSON being the easiest way (i.e. in the form {"latitude": 12.2, "longitude": 11.1}).
Your view will do the following:
Get latitude/longitude values from models
Convert to JSON format
Return a HTTPResponse object using render_to_response or whatever
On your client side, here is an example using the jQuery Javascript library to do an AJAX request:
<script type="text/javascript">
//Run When page first loads
map.setCenter(new f.LatLng{{lat_long}}, 11);
var updateLatLng = function () {
$.ajax({
type: "GET",
url: "/url/to/latlng/view",
data: "mapID=7", //Whatever extra parameters you need will go here
success: function(data) {
//This is run when we get data back from the server,
//If you send back the data in JSON format
//Then you can access the data using "data.latitude" and "data.longitude"
map.setCenter(new f.LatLng(data.latitude, data.longitude});
}
});
};
//Call updateLatLng every two seconds
window.setInterval(updateLatLng , 2000);
</script>
You're dealing with different points in time here.
Django renders template, calculates lat_long and feeds it in.
Rendered page is sent to client.
Browsers loads page and individual content resources, including your AJAX scripts.
AJAX eventually runs, fetches new lat_long from server and returns it to client.
Success function of AJAX request receives data and does something with it.
The point is that the value has long been set by the on page script before the AJAX request returns a new one. They're not really in competition here. If you want to change the map center based on the new value for lat_long, then just recall map.setCenter with the new value in your AJAX success method.
Related
I have a problem and hope you can help.
Ii have a status.PHP file containing a js.
STATUS.PHP
<? ..stuff... ?>
<html>
<head>
<title>BCM Status Page</title>
<script src="jquery-3.3.1.min.js"></script>
<script src="updater.js"></script>
</head>
<body bgcolor="#305c57" onload='init();'>
As you can see in the html ihave included a JS, during "onload" i'm calling the init() function of the javascript called updater.js
Now in the UPDATER.JS
function init() {
setInterval(read, 2000)
}
function read() {
$.ajax({
type: 'POST',
url: 'readDB.php',
dataType: 'jsonp',
success: function (data) {
console.log(data);
var json_obj = $.parseJSON(data);
console.log(json_obj[0].gwnumber);
},
error: function () {
console.log("Error loading data");
}
});
}
I'm doing an ajax call to the readDB.php that is working as intended, infact i have the correct value in the json_obj.
My question is: how can i get the json_obj value and pass it to the status.PHP file that is the one who's including the JS too?
Hope you can help. TY
Ok, there is a lot to say in this argument, but i will be the briefiest possible.
first things first
php and Javascript are two different programming language with a completely different paradigm.
The first is a back-end focused programming language;
Javascript instead is more front-end focused, just for entirety i have to mention that JS is used also for the backend part with a special eviroment called Node.js
back to the problem, the things that you are trying to do is not impossible but is excactly as you asked, your're idea (if i got it) was to pass the data from the js to the php like a parameter in a function...
the thing is that the php is elaborate and renderizated before in the server and the javascript is executed in the client, in the client web page there is no more footprint the php. This process is described very well at this link: http://php.net/manual/en/intro-whatis.php
The possible solution is:
FRONT-END(js): make another ajax call(request) to the same page that you are displaying with all the data that you want to elaborate.
BACK-END(php): controll if this request has been made, then access the data with the global variables $_POST & $_GET (depending on the type of the request), then elaborate this data.
if I can I suggest you to make a check if the manipulation that you want to do on those data need to be done in the server-side and not by the js!
Consider the order of execution:
User visits status.php
Browser requests status.php
Server executes status.php and sends response to browser
JS requests readDB.php
Browser requests readDB.php
Server executes readDB.php and sends response to browser
JS processes response
Go To 4
By the time you get to 7, it is too late to influence what happens at step 2.
You could make a new Ajax request to status.php and process the response in JS, but since status.php returns an entire HTML document, that doesn't make sense.
You could use location to load a new page using a URL that includes status.php and a query string with information from the Ajax response, but that would making using Ajax in the first place pointless.
You should probably change readDB.php to return *all** the data you need, and then using DOM methods (or jQuery wrappers around them) to modify the page the user is already looking at.
The simpliest and fastest (maybe not the sexiest way) to do it :
create global variable var respondData; in STATUS.PHP
within you ajax request on success function assign your data callback to it
respondData = data;
Now you have an access to it from every place in your code even when the ajax request is done. Just bare in mind to ensure you will try to access this variable after the page will fully load and after ajax will process the request. Otherwise you will get 'undefined'
This below is displaying Total racers on my website but its not updating live. I need to referesh the page to grab the new number from the database, so what's the simple way of updating it live with jquery/javascript without refreshing the page? Thanks a lot for taking the time to check my question and possibly answer.
<div id="stats">
<div id="racers">
<span><?=number_format($racers, 0, ' ', ' ')?></span>
RACERS
</div>
</div>
Jquery Ajax:
$.post('page.php', {
postVariable : value
}, function(data) {
//do something with data retrieved from php script
});
You set 'page.php' to a script that gets the data you want and echoes it.
You then retrieve what was echoed in the callback function(data);
So data will be the variable containing the value you need. You put this script in a
javascript function and call it when you need to make a request for information on the back-end.
If you have questions let me know. If you need more information on the ajax request you can find it here as well: api.jquery.com/jquery.post/
What you need to do this is the following:
1. Have an action in a controller that outputs the total number of racers
For example:
class Data extends CI_Controller {
public function GetTotalRacers() {
// This is dummy data. You need to replace this code with the correct
// number of racers retrieved from the database
echo 14;
}
}
Take note of where this action is. I'm assuming codeigniter will make the path something like /Data/GetTotalRacers in this case (that depends on how your route rules are configured).
2. Use JavaScript to ask the server for the data and display the result on the page
I recommend you have a method that runs every X number of seconds to refresh the total number of racers. To achieve this, you can use setInterval. Within the setInterval's function have an ajax call to your action. Finally, display the value that's returned from the server:
setInterval(function() {
$.ajax({
// Replace the url value with the correct url to access your action
url: '/Data/GetTotalRacers',
cache: false
})
.done(function( totalRacers ) {
$("#racers span").text(totalRacers);
});
}, 60000); // ex. Update every 60000ms
Note: I've never used codeigniter, but hopefully this description will help set you on the right path.
I have looked at a number of answers and other websites, but none answer my specific question. I have a webpage with "+" and "-" buttons, which should increment a variable called "pieFact". This variable must be updated dynamically without having to refresh the page. It should then be passed to my Django view each time the value is changed. This will be used to update the size of pie charts in a web map. I have the following:
<button type="button" id=bttnMinus onclick="pieFact=pieFact*0.9">-</button>
<button type="button" id=bttnPlus onclick="pieFact=pieFact*1.1">+</button></td>
<script type="text.javascript">
var pieFact=0;
</script>
How can I pass the value of "pieFact" to Django? Based on my limited knowledge, I think I may have to use AJAX post/get.
In order to keep from refreshing the page, yes, you will need AJAX. I usually don't like to suggest libraries too much in answers, however, in the interest of being easily cross-browser compatible, I would suggest the use of jQuery.
With jQuery it would be as simple as
Inside of your django template
<html>
...
<head>
<script>
var URL = "{% url 'my_view_that_updates_pieFact' %}";
</script>
</head>
...
Later on...
You'll need to either POST or GET the data to the server via AJAX. To be more RESTful, whenever I need to send data to the server I use POST. jQuery provides the $.post() convenience function to AJAX data to a url via POST. The three parameters are the URL, the data to send (as a JavaScript object; think python dictionaries if you're not too familiar with JavaScript), and a callback function once the server sends back a response.
<script>
function updatePieFact(){
var data = {'pieFact': pieFact};
$.post(URL, data, function(response){
if(response === 'success'){ alert('Yay!'); }
else{ alert('Error! :('); }
});
}
The .click() functions are basically the same thing as specifying onlick in the html attribute. Both click events update pieFact as you would expect and then call updatePieFact() to send the value of pieFact to the server.
$(document).ready(function(){
$('#bttnMinus').click(function(){
pieFact *= 0.9;
updatePieFact();
});
$('#bttnPlus').click(function(){
pieFact *= 1.1;
updatePieFact();
});
});
</script>
In views.py
Since I've used the $.post() function in the JavaScript, the request that Django is going to receive is going to have a method of "POST", so I check to make sure that the method is indeed POST (this means that if someone visits the URL for this view with something like a GET request, they won't update anything). Once I see that the request is, in fact, a POST, I check to see if the key 'pieFact' is in the dict request.POST.
Remember when I set the variable data in the javascript to {'pieFact': pieFact}? That javascript just becomes the request.POST python dictionary. So, if in the javascript I had instead used var data = {'hello': pieFact};, then I would be checking if 'hello' in request.POST instead. Once I see that pieFact is in the request.POST dictionary, I can get its value and then do something with it. If everything is successful, I return an HttpResponse with the string 'success'. This correlates with the check in javascript: if(response === 'success').
def my_view_that_updates_pieFact(request):
if request.method == 'POST':
if 'pieFact' in request.POST:
pieFact = request.POST['pieFact']
# doSomething with pieFact here...
return HttpResponse('success') # if everything is OK
# nothing went well
return HttpRepsonse('FAIL!!!!!')
Hopefully that will get you pointed in the right direction.
I'm very, very new to Javascript, and to web programming in general. I think that I'm misunderstanding something fundamental, but I've been unable to figure out what.
I have the following code:
function checkUserAuth(){
var userAuthHttpObject = new XMLHttpRequest();
var url = baseURL + "/userAuth";
userAuthHttpObject.open("POST",url,true);
userAuthHttpObject.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
userAuthHttpObject.onload=function(){
if (userAuthHttpObject.readyState == 4) {
var response = json.loads(userAuthHttpObject.responseText);
return response; //This is the part that doesn't work!
}
};
userAuthHttpObject.send(params);
}
I would love to call it from my page with something like:
var authResponse = checkUserAuth();
And then just do what I want with that data.
Returning a variable, however, just returns it to the userAuthObject, and not all the way back to the function that was originally called.
Is there a way to get the data out of the HttpObject, and into the page that called the function?
Working with AJAX requires wrapping your head around asynchronous behavior, which is different than other types of programming. Rather than returning values directly, you want to set up a callback function.
Create another JavaScript function which accepts the AJAX response as a parameter. This function, let's call it "takeAction(response)", should do whatever it needs to, perhaps print a failure message or set a value in a hidden field and submit a form, whatever.
then where you have "return response" put "takeAction(response)".
So now, takeAction will do whatever it was you would have done after you called "var authResponse = checkUserAuth();"
There are a couple of best practices you should start with before you continue to write the script you asked about
XMLHTTTPRequest() is not browser consistent. I would recommend you use a library such as mootools or the excellent jquery.ajax as a starting point. it easier to implement and works more consistently. http://api.jquery.com/jQuery.ajax/
content type is important. You will have have problems trying to parse json data if you used a form content type. use "application/json" if you want to use json.
true user authorization should be done on the server, never in the browser. I'm not sure how you are using this script, but I suggest you may want to reconsider.
Preliminaries out of the way, Here is one way I would get information from an ajax call into the page with jquery:
$.ajax({
//get an html chunk
url: 'ajax/test.html',
// do something with the html chunk
success: function(htmlData) {
//replace the content of <div id="auth">
$('#auth').html(htmlData);
//replace content of #auth with only the data in #message from
//the data we recieved in our ajax call
$('#auth').html( function() {
return $(htmlData).find('#message').text();
});
}
});
I have a page in which I am making an ajax call, which in turn gets forwarded to a jsp page and returns a table constructed in this jsp.
Till now this jsp used to return an html which the original page(table) used to append in a particular div. But now, we have a requirement that this jsp along with the table, returns some other info about the metadat of the query.
With this change, I would ideally not like to change the existing behaviour of some clients where they are just appending the html. But then, is there a way, in which the new pages which make this call can have both the html table(which can be appended) as well as metadata returned (which can be processed).
let me know if the question isn't clear enough.
Thanks!
The easiest and least destructive change would be to send it as response header.
In the servlet you can use HttpServletResponse#setHeader() to set a response header:
response.setHeader("X-Metadata", metadata);
// ...
(using a header name prefixed with X- is recommended for custom headers)
In JS you can use XMLHttpRequest#getResponseHeader() to get a response header:
var metadata = xhr.getResponseHeader('X-Metadata');
// ...
You can even set some JSON string in there so that (de)serialization is easy.