Develop Reference

Saving json data in a URL to browser memory on page load

I have a URL which contain some data in JSON format. I want to save this data in local browser memory on page load. Later I need to use this local copy as a source for my JQuery autocomplete. At the moment I'm pointing autocomplete source to this URL, so its calling that service very frequently.
Please help me to save the data in browser local memory and how to use it for jQuery autocomple.
Thank you.

If you really want to store it locally more permanently take a look at local storage
You should be able to do something like
$(document).ready(function {
$.get('http://example.com', function (data) {
localStorage.setItem('autocomplete', data.toString());
});
And then on any page you can use
var autocompleteData = JSON.parse(localStorage.getItem('autocomplete')
$('#myautocomplete').autocomplete({source: autocompleteData});
But it may simply be good enough just to declare a page scope variable and use that. That way it calls once per page load and you don't need to expire it.
<script>
var autocompleteSource;
$(document).ready(function {
$.get('http://example.com', function (data) {
autocompleteSource = JSON.parse(data);
});
$('#myautocomplete').autocomplete({source: autocompleteSource});
});
</script>
This assumes that you can parse the response into an array in the appropriate format.
Update based on comment:
I think you will still need to pass in the function as the source, as you are doing a contains search (indexOf(..) != -1).
Your autocompleteSource would contain all of the nested data: perhaps
$.get('http://example.com', function (data) {
autocompleteSource = [];
data.countries.map(function(itemCountry) {
itemCountry.cities.map(function(itemCity) {
itemCity.destinations.map(function(itemDestination {
autocompleteSource.push(itemDestination);
});
and then you would declare the method just working off the local data set
$('#myautocomplete').autocomplete(source : function (request, response){
var filtered = autocompleteSource.filter(function(item){
return item.toLowerCase().indexOf(request.term.toLowerCase()) > -1
});
response(filtered);
});

My App reads txt files even if they are deleted

I have developed an app that reads some data from a txt file.
jQuery.get('/mnt/sdcard/koinoxrista/File.txt',
function(data){
//do something
}
The strange thing is that since yesterday, even if I delete the txt file, my app still reads it...
The problem does not exist if I remove and reinstall my app.
How can I solve this issue?

Try to disable cache (docs)
jQuery.ajax({
url: '/mnt/sdcard/koinoxrista/File.txt',
cache: false,
success: function(data) {
//do something
}
});

It is stored in your app's cache memory every time you execute jQuery.get

JSON call giving value that is not actually in the .json file

I am a little new when it comes to JSON and Javascript , so please excuse me if if this is a stupid question, but I have run into a problem that is starting to drive me insane.
On a webpage I am including two scripts; jQuery and a file called "scripts2.js". In the same directory as scripts2.js, I have a JSON file; "settings.json". From within my "scripts2.js" file I am running he following code inside of a function.
var settingsPath = settings.json;
jQuery.getJSON(settingsPath, function (data){
jQuery.each(data, function(index){
console.log("!"+data[index].name);
/*unrelated other stuff */
});
});
Previously the settings.json file looked like this
[
{"name":"Standard Black"},
{"name":"Gold"},
{"name":"Silver"}
]
So naturally when I looked in the Chrome Dev Console the log would print out
!Standard Black
!Gold
!Silver
However, when testing what would happen upon editing my settings.json file I changed "name":"Gold" to "name":"Test".
[
{"name":"Standard Black"},
{"name":"Test"},
{"name":"Silver"}
]
After the json updates I tried refreshing the page but my console log is still printing out
!Standard Black
!Gold
!Silver
...
I am at a loss. I have no idea why the data being retrieved with jQuery.getJSON() is sending the data of my old settings.json even after the changes has been saved. I have perused my .php file (which is generating the HTML) , as well as my included javascript and there is no other mention of another json file or any sort of clone of my json file in any related directory.
I really have no idea what is going on and I am starting to go insane. Does anyone have an idea of what the issue might be?
I dont know if it matters but I am running a XAMPP stack on my localhost. All files (index.php, scripts2.js, and settings.json) are in a directory located inside XAMPP's htdocs folder.
EDIT: Thank you all for the speedy and thorough answers, many of you answered the question I was a bout to ask next. I really appreciate it!

This is because the browser is caching the file from your first request. Simply clear the cache and run it again and the new data will be retrieved.
UPDATE:
To prevent the browser from caching this file, change your AJAX settings like so:
jQuery.ajaxSetup({ cache: false });
Before you make the getJSON call

Try clearing web cache and restart local servers if you have not already

When using jQuery.ajax() instead of the shorthand method, you can disable caching like this:
jQuery.ajax(settingsPath, {cache: false})
jQuery will append a timestamp parameter to your request URL which changes with every request and therefore keeps the browser from caching the response.

To force the browser to get a new version each time you can use cache: false in jQuery.ajax()
$.ajax({
dataType: "json",
url: settingsPath,
cache: false,
success: function (data){
$.each(data, function(index){
console.log("!"+data[index].name);
});
}
});

Pass additional parameter to your requested url which value will change with every request.So,your browser will consider it as new request every time and will not cache the data.
var random = Math.round(new Date().getTime())
var settingsPath = 'settings.json&time=' + random;
jQuery.getJSON(settingsPath, function(data) {
});
});
You can use any algoritham that generate random new value everytime for random for every request.
OR
you can have same things with jQuery#Ajax method

jQuery.getJSON is a shorthand Ajax function, which is equivalent to:
$.ajax({
dataType: "json",
url: url,
data: data,
success: success
});
So, set the optional parameter cache to false (this value by default is always true):
$.ajax({
dataType: "json",
url: url,
data: data,
cache: false, // If set to false, it will force requested pages not to be cached by the browser
success: success
});
Therefore, your getJson becomes:
var settingsPath = settings.json;
jQuery.ajax({
dataType: "json",
url: settingsPath,
data: data,
cache: false,
success: function(data) {
jQuery.each(data, function (index) {
console.log("!" + data[index].name);
/*unrelated other stuff */
});
}
});

How to get a JSON string result from a database for later use

I am working on the backend for a webpage that displays EPG information for TV channels from a SQlite3 database. The data is provided by a PHP script echoing a JSON string. This itself works, executing the php program manually creates a JSON string of this format
[{"id":"0001","name":"RTL","frequency":"626000000"},{"id":...
I want to use these objects later to create HTML elements but the ajax function to get the string doesn't work. I have looked at multiple examples and tutorials but they all seemed to be focused more on having PHP return self contained HTML elements. The relevant js on my page is this:
var channelList;
$(document).ready(function() {
$.ajax({
url: 'channellookup.php',
dataType: "json",
success: function(data) {
console.log(data.success);
channelList = data;
}
});
});
However the channelList variable remains empty when inspected via console.
What am I doing wrong?

Please ensure that your PHP echoing the correct type of content.
To echo the JSON, please add the content-type in response header.
<?php
header(‘Content-type:text/json’); // To ensure output json type.
echo $your_json;
?>

It's because the variable is empty when the program runs. It is only populated once AJAX runs, and isn't updating the DOM when the variable is updated. You should use a callback and pass in the data from success() and use it where you need to.
Wrap the AJAX call in a function with a callback argument. Something like this:
function getChannels(callback){
$.ajax({
url: 'channellookup.php',
dataType: "json",
success: function(data) {
console.log(data);
if (typeof(callback) === 'function') {
callback(data);
}
},
error: function(data) {
if (typeof(callback) === 'function') {
callback(data);
}
}
});
}
Then use it when it becomes available. You should also use error() to help debug and it will quickly tell you if the error is on the client or server. This is slightly verbose because I'm checking to make sure callback is a function, but it's good practice to always check and fail gracefully.
getChannels(function(channels){
$('.channelDiv').html(channels.name);
$('.channelDiv2').html(channels.someOtherProperty);
});
I didn't test this, but this is how the flow should go. This SO post may be helpful.
EDIT: This is why frameworks like Angular are great, because you can quickly set watchers that will handle updating for you.

Assigning JSON object to variable from google sheets URL?

I want to be able to pull data from a google spreadsheet doc every 24hrs and use the values in my html page.
I have managed to get the JSON url for the cell I want to track, but I do not know how to get this JSON object into a javascript variable using the url.
I have searched around and tried using Jquery $.get() and $.getJSON() but I cant seem to get anything to work.
The url for the google spreadsheet data cell JSON is
https://spreadsheets.google.com/feeds/cells/1r56MJc7DVUVSkQ-cYdonqdSGXh5x8nRum4dIGMN89j0/1/public/values/R29C4?alt=json-in-script&callback=importGSS
I know this is probably simple but I am very new to working with JSON/ Javascript and have been struggling to work this out.
Thanks for any help :)

The data being returned is jsonp so you need to specify that in your Ajax request.
function getData() {
return $.ajax({
url: 'https://spreadsheets.google.com/feeds/cells/1r56MJc7DVUVSkQ-cYdonqdSGXh5x8nRum4dIGMN89j0/1/public/values/R29C4?alt=json-in-script&callback=importGSS',
dataType: 'jsonp',
jsonpCallback: 'importGSS'
})
}
And while you can assign the data to, say, a global variable this will only get you so far - the Ajax process is asynchronous and you won't be able to access the data until the process has finished:
var obj;
getData().done(function (data) {
obj = data;
});
// console.log(obj) here will return undefined as the process
// has not yet finished
Much better to grab the data and do something with it:
function doSomethingWithData(data) {
console.log(data);
}
getData().done(function (data) {
doSomethingWithData(data);
});
Or even simpler:
getData().done(doSomethingWithData);