I'm using a tableau web connector to download stock price. The source code is following:
<html>
<meta http-equiv="Cache-Control" content="no-store" />
<head>
<title>Stock Quote Connector-Tutorial</title>
<script src="https://connectors.tableau.com/libs/tableauwdc-1.1.1.js" type="text/javascript"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
(function() {
function buildUri(tickerSymbol, startDate, endDate) {
var startDateStr = getFormattedDate(startDate);
var endDateStr = getFormattedDate(endDate);
var queryStatement = 'select * from yahoo.finance.historicaldata where symbol = "' +
tickerSymbol +
'" and startDate = "' + startDateStr +
'" and endDate = "' + endDateStr + '"';
var uri = 'http://query.yahooapis.com/v1/public/yql?q=' +
encodeURIComponent(queryStatement) +
"&env=http%3A%2F%2Fdatatables.org%2Falltables.env&format=json";
return uri;
}
function getFormattedDate(date) {
// Return a date in the format YYYY-MM-DD
return date.getUTCFullYear() +
'-' +
makeTwoDigits(date.getUTCMonth() + 1) +
'-' +
makeTwoDigits(date.getUTCDate());
}
function makeTwoDigits(num) {
// Pad a digit to be two digits with leading zero
return num <= 9 ? "0" + num.toString() : num.toString();
}
var myConnector = tableau.makeConnector();
myConnector.getColumnHeaders = function() {
var fieldNames = ['Ticker', 'Day', 'Close'];
var fieldTypes = ['string', 'date', 'float'];
tableau.headersCallback(fieldNames, fieldTypes);
}
myConnector.getTableData = function(lastRecordToken) {
var dataToReturn = [];
var hasMoreData = false;
// Get parameter values and build YQL query
var ticker = tableau.connectionData;
var endDate = new Date();
var startDate = new Date();
startDate.setYear(endDate.getFullYear() - 1);
//startDate.setYear(startDate.getFullYear() - 1);
//startDate.setYear(startDate.getFullYear() - 1);
//startDate.setYear(startDate.getFullYear() - 1);
var connectionUri = buildUri(ticker, startDate, endDate);
var xhr = $.ajax({
url: connectionUri,
dataType: 'json',
success: function (data) {
if (data.query.results) {
var quotes = data.query.results.quote;
var ii;
for (ii = 0; ii < quotes.length; ++ii) {
var entry = {'Ticker': quotes[ii].Symbol,
'Day': quotes[ii].Date,
'Close': quotes[ii].Close};
dataToReturn.push(entry);
}
tableau.dataCallback(dataToReturn, lastRecordToken, false);
}
else {
tableau.abortWithError("No results found for ticker symbol: " + ticker);
}
},
error: function (xhr, ajaxOptions, thrownError) {
tableau.log("Connection error: " + xhr.responseText + "\n" + thrownError);
tableau.abortWithError("Error while trying to connect to the Yahoo stock data source.");
}
});
}
tableau.registerConnector(myConnector);
})();
$(document).ready(function() {
$("#submitButton").click(function() {
var tickerSymbol = $('#ticker').val().trim();
if (tickerSymbol) {
tableau.connectionName = "Stock Data for " + tickerSymbol;
tableau.connectionData = tickerSymbol;
tableau.submit();
}
});
});
</script>
</head>
<body>
<p>Enter a stock ticker symbol: <input type="text" id="ticker" /></p>
<p><button type="button" id="submitButton">Get the Data</button></p>
</body>
</html>
The code is workable when we just want to download 1 year data, but if we change the time longer than 1 year(enddate.year - startdate.year > 1), it is not workable.
After debugging the code, I found the issue comes from YQL query:
http://query.yahooapis.com/v1/public/yql?q=select * from yahoo.finance.historicaldata where symbol = "AAPL" and startDate = "2014-08-24" and endDate = "2016-11-23"&env=http%3A%2F%2Fdatatables.org%2Falltables.env&format=json
when startDate = "2014-08-24" and endDate = "2016-11-23" is longer than 15 month, YQL will return null. I'm trying to fix this issue. If it is python or java, the problem is not hard, first check whether the duration is longer than 1 year, if so, get 1 year result and do the same for rest n-1 year. But this tableau code makes me stuck with it. I have to make the code workable with tableau, which makes me unable to proceed due to lack of knowledge about both js and tableau.
Can any one advise on this issue? My objective is to make the code workable for >10 years for stock symbol like AAPL.
Thanks in advance.
I don't believe YQL supports queries for longer than 15 months or so. Limits like these are fairly common when working with APIs. What you want to do from a web data connector standpoint is to implement paging.
The high level idea is that your getTableData function of your WDC will execute multiple times, and each time, it will gather a single page of data, which is then passed to Tableau. For example, here's how you could get multiple years worth of data in your example:
myConnector.getTableData = function(lastRecordToken) {
var dataToReturn = [];
var hasMoreData = false;
// Get parameter values and build YQL query
var ticker = tableau.connectionData;
var endDate = new Date();
var startDate = new Date();
var maxYear = 5;
var yearOffset = lastRecordToken || 0;
endDate.setYear(endDate.getFullYear() - (yearOffset));
startDate.setYear(endDate.getFullYear() - 1);
var connectionUri = buildUri(ticker, startDate, endDate);
var xhr = $.ajax({
url: connectionUri,
dataType: 'json',
success: function (data) {
if (data.query.results) {
var quotes = data.query.results.quote;
var ii;
for (ii = 0; ii < quotes.length; ++ii) {
var entry = {'Ticker': quotes[ii].Symbol,
'Day': quotes[ii].Date,
'Close': quotes[ii].Close};
dataToReturn.push(entry);
}
var hasMoreData = !(yearOffset == maxYear);
tableau.dataCallback(dataToReturn, yearOffset + 1, hasMoreData)
}
else {
tableau.abortWithError("No results found for ticker symbol: " + ticker);
}
},
error: function (xhr, ajaxOptions, thrownError) {
tableau.log("Connection error: " + xhr.responseText + "\n" + thrownError);
tableau.abortWithError("Error while trying to connect to the Yahoo stock data source.");
}
});
}
tableau.registerConnector(myConnector);
})();
This example uses the two extra parameters of the dataCallback function to implement paging. The documentation for paging in v1 of the web data connector API can be found here: http://onlinehelp.tableau.com/current/api/wdc/en-us/help.htm#WDC/wdc_paging.htm%3FTocPath%3DAdditional%2520Concepts%7C_____2
Additionally, if you are able to use v2 of the WDC API (usable in Tableau 10 and later), I would highly recommend it. The paging model in V2 is more flexible and easier to use.
The snoowrap library returns a promise when a function a call is made using it. I would like for node to wait until the call is complete and then execute its callback function. How can I do that? I've tried different forms of using setTimeout, wait.for library, and other solutions but none have worked.
while(1){
for (var i = 0; i < allowableTimes.length; i++) {
if (new Date().getTime() == allowableTimes[i].getTime()) {
reddit.getHot('aww', {limit: 1}).then(sendToSlack);
}
}
}
function sendToSlack(res){
var url = res[0].url;
var title = res[0].title;
bot.sendWebhook({
username: "bawwt",
icon_emoji: ":smile_cat:",
text: "<" + url + "|" + title + ">",
channel: "#random"
});
}
SOLVED: Here is the solution below that worked for me based on the code in the accepted answer:
if (!err) {
reddit.getHot('aww', {limit: 1}).then(handleReddit);
}
});
function handleReddit(res) {
for (var i = 0; i < allowableTimes.length; i++) {
if (validTime(allowableTimes[i])) {
sendToSlack(res);
}
}
queryReddit();
}
function validTime(allowableTime) {
var date = new Date();
var hour = date.getHours();
var minute = date.getMinutes();
var allowableHour = allowableTime.getHours();
var allowableMinute = allowableTime.getMinutes();
return hour == allowableHour && minute == allowableMinute;
}
function queryReddit() {
setTimeout(function() {reddit.getHot('aww', {limit: 1}).then(handleReddit);}, 60000);
}
function sendToSlack(res){
var url = res[0].url;
var title = res[0].title;
bot.sendWebhook({
username: "bawwt",
icon_emoji: ":smile_cat:",
text: "<" + url + "|" + title + ">",
channel: "#random"
});
}
I believe the reason your callback never gets called is because you never give the node runtime a chance to do that. It's a single thread and you are infinitely using it up with your while(1). It will not have a chance to actually handle the resolving network call that the promise responds to as you are keeping the thread busy with more
As mentioned in the comment: In node, you shouldn't block the rest of the server on a callback. Instead, you should make sendToSlack a recursive function that deals with the callback and fires off another call to reddit.getHot() and get rid of the loop
Conceptual code:
var allowableTimes = 20;
var times = 0;
function handleReddit(res)
{
sendToSlack(res);
times = times + 1;
if(times < allowableTimes)
{
reddit.getHot('aww', {limit: 1}).then(handleReddit);
}
}
reddit.getHot('aww', {limit: 1}).then(handleReddit);
Just off hand code
How can I create a JavaScript page that will detect the user’s internet speed and show it on the page? Something like “your internet speed is ??/?? Kb/s”.
It's possible to some extent but won't be really accurate, the idea is load image with a known file size then in its onload event measure how much time passed until that event was triggered, and divide this time in the image file size.
Example can be found here: Calculate speed using javascript
Test case applying the fix suggested there:
//JUST AN EXAMPLE, PLEASE USE YOUR OWN PICTURE!
var imageAddr = "http://www.kenrockwell.com/contax/images/g2/examples/31120037-5mb.jpg";
var downloadSize = 4995374; //bytes
function ShowProgressMessage(msg) {
if (console) {
if (typeof msg == "string") {
console.log(msg);
} else {
for (var i = 0; i < msg.length; i++) {
console.log(msg[i]);
}
}
}
var oProgress = document.getElementById("progress");
if (oProgress) {
var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");
oProgress.innerHTML = actualHTML;
}
}
function InitiateSpeedDetection() {
ShowProgressMessage("Loading the image, please wait...");
window.setTimeout(MeasureConnectionSpeed, 1);
};
if (window.addEventListener) {
window.addEventListener('load', InitiateSpeedDetection, false);
} else if (window.attachEvent) {
window.attachEvent('onload', InitiateSpeedDetection);
}
function MeasureConnectionSpeed() {
var startTime, endTime;
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
showResults();
}
download.onerror = function (err, msg) {
ShowProgressMessage("Invalid image, or error downloading");
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = imageAddr + cacheBuster;
function showResults() {
var duration = (endTime - startTime) / 1000;
var bitsLoaded = downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
ShowProgressMessage([
"Your connection speed is:",
speedBps + " bps",
speedKbps + " kbps",
speedMbps + " Mbps"
]);
}
}
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>
Quick comparison with "real" speed test service showed small difference of 0.12 Mbps when using big picture.
To ensure the integrity of the test, you can run the code with Chrome dev tool throttling enabled and then see if the result matches the limitation. (credit goes to user284130 :))
Important things to keep in mind:
The image being used should be properly optimized and compressed. If it isn't, then default compression on connections by the web server might show speed bigger than it actually is. Another option is using uncompressible file format, e.g. jpg. (thanks Rauli Rajande for pointing this out and Fluxine for reminding me)
The cache buster mechanism described above might not work with some CDN servers, which can be configured to ignore query string parameters, hence better setting cache control headers on the image itself. (thanks orcaman for pointing this out))
The bigger the image size is, the better. Larger image will make the test more accurate, 5 mb is decent, but if you can use even a bigger one it would be better.
Well, this is 2017 so you now have Network Information API (albeit with a limited support across browsers as of now) to get some sort of estimate downlink speed information:
navigator.connection.downlink
This is effective bandwidth estimate in Mbits per sec. The browser makes this estimate from recently observed application layer throughput across recently active connections. Needless to say, the biggest advantage of this approach is that you need not download any content just for bandwidth/ speed calculation.
You can look at this and a couple of other related attributes here
Due to it's limited support and different implementations across browsers (as of Nov 2017), would strongly recommend read this in detail
I needed a quick way to determine if the user connection speed was fast enough to enable/disable some features in a site I’m working on, I made this little script that averages the time it takes to download a single (small) image a number of times, it's working pretty accurately in my tests, being able to clearly distinguish between 3G or Wi-Fi for example, maybe someone can make a more elegant version or even a jQuery plugin.
var arrTimes = [];
var i = 0; // start
var timesToTest = 5;
var tThreshold = 150; //ms
var testImage = "http://www.google.com/images/phd/px.gif"; // small image in your server
var dummyImage = new Image();
var isConnectedFast = false;
testLatency(function(avg){
isConnectedFast = (avg <= tThreshold);
/** output */
document.body.appendChild(
document.createTextNode("Time: " + (avg.toFixed(2)) + "ms - isConnectedFast? " + isConnectedFast)
);
});
/** test and average time took to download image from server, called recursively timesToTest times */
function testLatency(cb) {
var tStart = new Date().getTime();
if (i<timesToTest-1) {
dummyImage.src = testImage + '?t=' + tStart;
dummyImage.onload = function() {
var tEnd = new Date().getTime();
var tTimeTook = tEnd-tStart;
arrTimes[i] = tTimeTook;
testLatency(cb);
i++;
};
} else {
/** calculate average of array items then callback */
var sum = arrTimes.reduce(function(a, b) { return a + b; });
var avg = sum / arrTimes.length;
cb(avg);
}
}
As I outline in this other answer here on StackOverflow, you can do this by timing the download of files of various sizes (start small, ramp up if the connection seems to allow it), ensuring through cache headers and such that the file is really being read from the remote server and not being retrieved from cache. This doesn't necessarily require that you have a server of your own (the files could be coming from S3 or similar), but you will need somewhere to get the files from in order to test connection speed.
That said, point-in-time bandwidth tests are notoriously unreliable, being as they are impacted by other items being downloaded in other windows, the speed of your server, links en route, etc., etc. But you can get a rough idea using this sort of technique.
Even though this is old and answered, i´d like to share the solution i made out of it 2020 base on Shadow Wizard Says No More War´s solution
I just merged it into an object that comes with the flexibility to run at anytime and run a callbacks if the specified mbps is higher or lower the measurement result.
you can start the test anywhere after you included the testConnectionSpeed Object by running the
/**
* #param float mbps - Specify a limit of mbps.
* #param function more(float result) - Called if more mbps than specified limit.
* #param function less(float result) - Called if less mbps than specified limit.
*/
testConnectionSpeed.run(mbps, more, less)
for example:
var testConnectionSpeed = {
imageAddr : "https://upload.wikimedia.org/wikipedia/commons/a/a6/Brandenburger_Tor_abends.jpg", // this is just an example, you rather want an image hosted on your server
downloadSize : 2707459, // Must match the file above (from your server ideally)
run:function(mbps_max,cb_gt,cb_lt){
testConnectionSpeed.mbps_max = parseFloat(mbps_max) ? parseFloat(mbps_max) : 0;
testConnectionSpeed.cb_gt = cb_gt;
testConnectionSpeed.cb_lt = cb_lt;
testConnectionSpeed.InitiateSpeedDetection();
},
InitiateSpeedDetection: function() {
window.setTimeout(testConnectionSpeed.MeasureConnectionSpeed, 1);
},
result:function(){
var duration = (endTime - startTime) / 1000;
var bitsLoaded = testConnectionSpeed.downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
if(speedMbps >= (testConnectionSpeed.max_mbps ? testConnectionSpeed.max_mbps : 1) ){
testConnectionSpeed.cb_gt ? testConnectionSpeed.cb_gt(speedMbps) : false;
}else {
testConnectionSpeed.cb_lt ? testConnectionSpeed.cb_lt(speedMbps) : false;
}
},
MeasureConnectionSpeed:function() {
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
testConnectionSpeed.result();
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = testConnectionSpeed.imageAddr + cacheBuster;
}
}
// start test immediatly, you could also call this on any event or whenever you want
testConnectionSpeed.run(1.5, function(mbps){console.log(">= 1.5Mbps ("+mbps+"Mbps)")}, function(mbps){console.log("< 1.5Mbps("+mbps+"Mbps)")} )
I used this successfuly to load lowres media for slow internet connections. You have to play around a bit because on the one hand, the larger the image, the more reasonable the test, on the other hand the test will take way much longer for slow connection and in my case I especially did not want slow connection users to load lots of MBs.
The image trick is cool but in my tests it was loading before some ajax calls I wanted to be complete.
The proper solution in 2017 is to use a worker (http://caniuse.com/#feat=webworkers).
The worker will look like:
/**
* This function performs a synchronous request
* and returns an object contain informations about the download
* time and size
*/
function measure(filename) {
var xhr = new XMLHttpRequest();
var measure = {};
xhr.open("GET", filename + '?' + (new Date()).getTime(), false);
measure.start = (new Date()).getTime();
xhr.send(null);
measure.end = (new Date()).getTime();
measure.len = parseInt(xhr.getResponseHeader('Content-Length') || 0);
measure.delta = measure.end - measure.start;
return measure;
}
/**
* Requires that we pass a base url to the worker
* The worker will measure the download time needed to get
* a ~0KB and a 100KB.
* It will return a string that serializes this informations as
* pipe separated values
*/
onmessage = function(e) {
measure0 = measure(e.data.base_url + '/test/0.bz2');
measure100 = measure(e.data.base_url + '/test/100K.bz2');
postMessage(
measure0.delta + '|' +
measure0.len + '|' +
measure100.delta + '|' +
measure100.len
);
};
The js file that will invoke the Worker:
var base_url = PORTAL_URL + '/++plone++experimental.bwtools';
if (typeof(Worker) === 'undefined') {
return; // unsupported
}
w = new Worker(base_url + "/scripts/worker.js");
w.postMessage({
base_url: base_url
});
w.onmessage = function(event) {
if (event.data) {
set_cookie(event.data);
}
};
Code taken from a Plone package I wrote:
https://github.com/collective/experimental.bwtools/blob/master/src/experimental/bwtools/browser/static/scripts/
It's better to use images for testing the speed. But if you have to deal with zip files, the below code works.
var fileURL = "your/url/here/testfile.zip";
var request = new XMLHttpRequest();
var avoidCache = "?avoidcache=" + (new Date()).getTime();;
request.open('GET', fileURL + avoidCache, true);
request.responseType = "application/zip";
var startTime = (new Date()).getTime();
var endTime = startTime;
request.onreadystatechange = function () {
if (request.readyState == 2)
{
//ready state 2 is when the request is sent
startTime = (new Date().getTime());
}
if (request.readyState == 4)
{
endTime = (new Date()).getTime();
var downloadSize = request.responseText.length;
var time = (endTime - startTime) / 1000;
var sizeInBits = downloadSize * 8;
var speed = ((sizeInBits / time) / (1024 * 1024)).toFixed(2);
console.log(downloadSize, time, speed);
}
}
request.send();
This will not work very well with files < 10MB. You will have to run aggregated results on multiple download attempts.
thanks to Punit S answer, for detecting dynamic connection speed change, you can use the following code :
navigator.connection.onchange = function () {
//do what you need to do ,on speed change event
console.log('Connection Speed Changed');
}
Improving upon John Smith's answer, a nice and clean solution which returns a Promise and thus can be used with async/await. Returns a value in Mbps.
const imageAddr = 'https://upload.wikimedia.org/wikipedia/commons/a/a6/Brandenburger_Tor_abends.jpg';
const downloadSize = 2707459; // this must match with the image above
let startTime, endTime;
async function measureConnectionSpeed() {
startTime = (new Date()).getTime();
const cacheBuster = '?nnn=' + startTime;
const download = new Image();
download.src = imageAddr + cacheBuster;
// this returns when the image is finished downloading
await download.decode();
endTime = (new Date()).getTime();
const duration = (endTime - startTime) / 1000;
const bitsLoaded = downloadSize * 8;
const speedBps = (bitsLoaded / duration).toFixed(2);
const speedKbps = (speedBps / 1024).toFixed(2);
const speedMbps = (speedKbps / 1024).toFixed(2);
return Math.round(Number(speedMbps));
}
I needed something similar, so I wrote https://github.com/beradrian/jsbandwidth. This is a rewrite of https://code.google.com/p/jsbandwidth/.
The idea is to make two calls through Ajax, one to download and the other to upload through POST.
It should work with both jQuery.ajax or Angular $http.
//JUST AN EXAMPLE, PLEASE USE YOUR OWN PICTURE!
var imageAddr = "https://i.ibb.co/sPbbkkZ/pexels-lisa-1540258.jpg";
var downloadSize = 10500000; //bytes
function ShowProgressMessage(msg) {
if (console) {
if (typeof msg == "string") {
console.log(msg);
} else {
for (var i = 0; i < msg.length; i++) {
console.log(msg[i]);
}
}
}
var oProgress = document.getElementById("progress");
if (oProgress) {
var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");
oProgress.innerHTML = actualHTML;
}
}
function InitiateSpeedDetection() {
ShowProgressMessage("Loading the image, please wait...");
window.setTimeout(MeasureConnectionSpeed, 1);
};
if (window.addEventListener) {
window.addEventListener('load', InitiateSpeedDetection, false);
} else if (window.attachEvent) {
window.attachEvent('onload', InitiateSpeedDetection);
}
function MeasureConnectionSpeed() {
var startTime, endTime;
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
showResults();
}
download.onerror = function (err, msg) {
ShowProgressMessage("Invalid image, or error downloading");
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = imageAddr + cacheBuster;
function showResults() {
var duration = (endTime - startTime) / 1000;
var bitsLoaded = downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
ShowProgressMessage([
"Your connection speed is:",
speedBps + " bps",
speedKbps + " kbps",
speedMbps + " Mbps"
]);
}
}
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>
Mini snippet:
var speedtest = {};
function speedTest_start(name) { speedtest[name]= +new Date(); }
function speedTest_stop(name) { return +new Date() - speedtest[name] + (delete
speedtest[name]?0:0); }
use like:
speedTest_start("test1");
// ... some code
speedTest_stop("test1");
// returns the time duration in ms
Also more tests possible:
speedTest_start("whole");
// ... some code
speedTest_start("part");
// ... some code
speedTest_stop("part");
// returns the time duration in ms of "part"
// ... some code
speedTest_stop("whole");
// returns the time duration in ms of "whole"
I have a code to put two cameras on my site:
$(document).ready(function(){
var m;
var index;
var IP;
var port;
var name;
var user;
var password;
var image_old;
var image_new;
var cameraFeed;
var topImage;
var urls = [];
$.ajax({
type: "GET",
url: "json.htm?type=cameras",
dataType: "JSON",
async : false,
success: function(data) {
for(m=0; m<=1; m++){
index = data.result[m].idx;
IP = data.result[m].Address;
port = data.result[m].Port;
name = data.result[m].Name;
user = data.result[m].Username;
password = data.result[m].Password;
image_old = data.result[m].ImageURL;
image_new = image_old.replace("#USERNAME", user).replace("#PASSWORD", password);
cameraFeed = "http://" + IP + ":" + port + "/" + image_new;
alert(cameraFeed + m);
urls.push(cameraFeed);
}
setInterval(function() {
var d = Date.now();
$.each(urls, function(i, url) {
$('#topImage' + i).attr('src', url + "×tamp=" + d);
});
}, 100);
},
error: function(data) {
alert("Error")
}
});
});
And html code:
<img id="topImage0" width="640px">
<img id="topImage1" width="640px">
I can not create a script to make setinterval work for both imgs. It works only for one of them. Any suggestions how to make it works ?
Set interval works only for one img.
To give you an idea how to structure your application code:
Get the data from the server
Create the URLs from data
Update each image every X milliseconds with those URLs
In code:
$.ajax({...}).done(function(data) { // get data from server
// create URLs
var urls = [];
for (var m = 0; m < 2; m++) { // why not iterate over data.results?
var cameraFeed;
// build cameraFeed ...
urls.push(cameraFeed);
}
// Update images
setInterval(function() {
var d = Date.now();
$.each(urls, function(i, url) {
$('#topImage' + i).attr('src', url + "×tamp=" + d);
});
}, 100);
});
Of course this can still be approved, but that should point you into the right direction. Note in particular that it is unnecessary to have a setInterval for each image. Just let a single interval update all images.
Especially the for loop can be approved upon. I don't know how many results data.results has and if you only want to get the first two, but this is an excellent use case for Array#map:
var urls = data.results.map(function(result) {
// ...
return cameraFeed;
});
My code loads new data when user reaches bottom of the page successfully but still when all posts from DB are loaded code tries to get more posts which results the page to stuck for several seconds. What i need is mechanism to detect when the last post has been loaded from DB and prevent code from executing.
function yHandler(){
var id=$(".output:last").attr("id");
var split = id.split("output");
var newid=split[1];
var awrap = document.getElementById('awrap');
var contentHeight = awrap.offsetHeight;
var yOffset = window.pageYOffset;
var y = yOffset + window.innerHeight;
var sesid=$("#sesid").val();
if(y >= contentHeight){
// Ajax call to get more dynamic data goes here
$.ajax({
url:"load.php",
type:"POST",
data:'did=' + did + '&newid=' + newid + '&id=' + id + "&sesid=" + sesid,
success:function(data){
$("#newdata").append(data);
});
} ///if end
} /// FUNC END
window.onscroll = yHandler;
load.php //
$osql=mysql_query("SELECT * FROM answer WHERE respond IS NOT NULL AND question_id='$did' AND id < '$newid' and pinned = '0' ORDER BY resp_time DESC LIMIT 5");
/// while loop which fetches data is below
If you don't want to or need to handle the case that other posts could show up via other means while the user is on this web page, then you can just set a flag when you got no more posts and check that flag and avoid the call to load.php if that flag is set.
// flag so we know when there are no more posts
var noMorePosts = false;
function yHandler(){
var id=$(".output:last").attr("id");
var split = id.split("output");
var newid=split[1];
var awrap = document.getElementById('awrap');
var contentHeight = awrap.offsetHeight;
var yOffset = window.pageYOffset;
var y = yOffset + window.innerHeight;
var sesid=$("#sesid").val();
if(!noMorePosts && y >= contentHeight){
// Ajax call to get more dynamic data goes here
$.ajax({
url:"load.php",
type:"POST",
data:'did=' + did + '&newid=' + newid + '&id=' + id + "&sesid=" + sesid,
success:function(data){
// pseudo code check to see if data was empty
// you fill in the actual test here
if (nothing in data) {
noMorePosts = true;
} else {
$("#newdata").append(data);
}
});
}
}
You could return from backend also the timestamp of the execution, then in client ask for this timestamp to retrieve or not data again. Just like caching works.
(I'll give you other alternative in a minute)
This could be another way (cache by request data):
function yHandler(){
yHandler.lastRequest = yHandler.lastRequest || null;
var id=$(".output:last").attr("id");
var split = id.split("output");
var newid=split[1];
var awrap = document.getElementById('awrap');
var contentHeight = awrap.offsetHeight;
var yOffset = window.pageYOffset;
var y = yOffset + window.innerHeight;
var sesid=$("#sesid").val();
if(y >= contentHeight){
// Ajax call to get more dynamic data goes here
var newRequest = 'did=' + did + '&newid=' + newid + '&id=' + id + "&sesid=" + sesid;
if(newRequest != yHandler.lastRequest){
$.ajax({
url:"load.php",
type:"POST",
data: yHandler.lastData,
success:function(data){
$("#newdata").append(data);
yHandler.lastData = newRequest; //Save the last request data
}
});
}
}
});
Basically, the above code saves the last request data. If in the next scroll it hasn't changed, then don't perform the ajax call.
Hope this helps. Cheers