I'm having some troubles with an iOS Smart App Banner, which I'm trying to add through JavaScript.
The actual smartbanner is as simple as adding this little block to the head of the HTML:
<meta name="apple-itunes-app" content="app-id=375380948">
Unfortunately, I'm quite restricted in the way I can upload my script. I can't change the HTML directly, so I'll do it through our Tag Manager, which basically does it through JavaScript. But it turns out that this doesn't work.
I've tried to simplify the case for testing:
Hardcoded tag in the HTML: works (as expected)
<meta name="apple-itunes-app" content="app-id=375380948">
Inserted with JavaScript directly when the document is ready: works
$(document).ready(function(){
$("head").append('<meta name="apple-itunes-app" content="app-id=375380948">');
});
Inserted with JavaScript, after a setTimeout delay: DOES NOT WORK
$(document).ready(function(){
setTimeout(showBanner, 1); //after 1 millisecond
});
function showBanner(){
$("head").append('<meta name="apple-itunes-app" content="app-id=375380948">');
}
Can anyone confirm or explain why this delayed JavaScript doesn't work?
Important: for testing open the page on an actual iOS device!
Desktop Safari/Chrome or iOS emulator won't work.
Also, don't close the banner, because it won't show up a second time.
UPDATE:
I've added some examples without jQuery, so plain 'ol JavaScript. But the results are the same. As soon as we wait for a setTimeout() the Smart App Banner fails to load.
Vanilla JavaScript - direct execution. works
showBanner();
function showBanner() {
var meta = document.createElement("meta");
meta.name = "apple-itunes-app";
meta.content = "app-id=375380948";
document.head.appendChild(meta);
}
Vanilla JavaScript - delayed execution. DOES NOT WORK
setTimeout(showBanner, 1);
function showBanner() {
var meta = document.createElement("meta");
meta.name = "apple-itunes-app";
meta.content = "app-id=375380948";
document.head.appendChild(meta);
}
UPDATE 2:
The exact same unfortunate behavior can be observed when loading the script asynchronously
async loading. DOES NOT WORK
<script src="async.js" async></script>
Which then calls the same vanilla JavaScript with direct execution
showBanner();
function showBanner() {
var meta = document.createElement("meta");
meta.name = "apple-itunes-app";
meta.content = "app-id=375380948";
document.head.appendChild(meta);
}
CONCLUSION:
I can only conclude that iOS Safari only looks for the smartbanner the HTML in the primary thread. And that makes me sad :-(
Only the directly available HTML, or HTML that is added synchronously through JavaScript.
But no a-sync action is allowed, be it loading the JavaScript asynchronously, or using setTimeout() (or an other construct that uses eval())
Since it is not possible to have safari show the native banner if it is inserted after the page load (As tested above, and confirmed by apple), the only viable workaround is not to use the native smartbanner, but to create your own.
For instance with a javascript plugin like this
As of April 2017, the smart banner will show up if added later via JavaScript.
Related
I'm currently writing a little program that generates an html file and opens it with the default browser to start multiple downloads.
I don't want to open a tab/window for every download, so creating hidden iframes for the downloads seemed like a good solution.
I'm using onload on the iframes to find out if the download prompts for each download have shown up yet. This approach seems to be very unreliable in the Internet Explorer though.
So I'm wondering if there is there a way to fix this or maybe a better approach?
(Without libraries please.)
Here is my html/js code:
<!DOCTYPE html>
<!-- saved from url=(0016)http://localhost -->
<html><head>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta content="utf-8" http-equiv="encoding">
<title>Downloads</title>
<script>
"use strict";
var downloadsInfo = {
"http://download-installer.cdn.mozilla.net/pub/firefox/releases/26.0/win32/en-US/Firefox%20Setup%2026.0.exe":"Status: Connecting",
"http://download.piriform.com/ccsetup410.exe":"Status: Connecting"
};
var i = 0;
var iv = setInterval(function() {
i = ++i % 4;
var j = 0;
var finished = true;
for (var key in downloadsInfo) {
var value = downloadsInfo[key];
if (value != "Status: Download Started!") {
value = value+Array(i+1).join(".");
finished = false;
}
document.getElementsByTagName("div")[j].innerHTML = key+"<br/>"+value;
j = j+1;
}
if (finished) {
alert('Done! You can close this window/tab now.');
clearInterval(iv);
}
}, 800);
</script>
</head><body>
<h3>Please wait for your downloads to start and do not reload this site.</h3>
<div></div> <br/><br/>
<div></div> <br/><br/>
<iframe src="http://download-installer.cdn.mozilla.net/pub/firefox/releases/26.0/win32/en-US/Firefox%20Setup%2026.0.exe" onload="downloadsInfo['http://download-installer.cdn.mozilla.net/pub/firefox/releases/26.0/win32/en-US/Firefox%20Setup%2026.0.exe'] = 'Status: Download Started!';" style="display:none"></iframe>
<iframe src="http://download.piriform.com/ccsetup410.exe" onload="downloadsInfo['http://download.piriform.com/ccsetup410.exe'] = 'Status: Download Started!';" style="display:none"></iframe>
</body></html>
Quite simply you can't know whether a native browser download started. Every browser has different ways this is handled, the user may set up his browser to prompt the location or he might just let it auto download to the Downloads folder (the default in most browsers nowadays). If he's prompting for a location he might cancel by mistake, yet your setup would still claim the download started. So, no, there is no way whatsoever to reliably inform the user that they can close a tab once all downloads are started/finished... provided that you use the native browser download mechanism.
The way to achieve this effect would be possibly by first downloading the file using Javascript (requiring you to have access to those files, hotlinking to third party files is of course not an option then). To see this in action try downloading a file from mega.nz. I was planning on writing up how to do this by hand, but there is already a nice (quite outdated) answer outlining this.
If the intention is only to ensure that the download has started you could implement a trigger on the back end to note when the file has been accessed. In it's simplest form this would look like:
Page download.html requests file.php?location=[...]&randomHash=1234
Once file.php is actually loaded it will set a flag in memory or the database that randomHash id 1234 has started.
file.php redirects the page with a 302 header to the actual file location.
download.html checks periodically using Ajax whether flag randomHash=1234 has been raised. If so it knows the download has started.
Indeed IE is reported to not always behave nicely with the onload event handler of iframes. There is an active bug tracker record opened.
The problem is discussed in a number of places around the web, and what seems to be the most reliable solution is to have an indirect download with nested iframes: the iframe loads a HTML file with an iframe that loads the file to download. The reason for that is that IE does not seem to like iframes that point to something else than HTML. So if you have the possibility to do that in your program:
For each file to download, generate a HTML file with a body that looks like this:
<iframe src="http://filetodownload.exe" style="display:none"></iframe>
Store this file in a temporary folder, e.g. C:\tmp\filetodownload.html
In your "master" generated HTML file, replace the iframe source with this intermediate file:
<iframe src="C:\tmp\filetodownload.html"
onload="downloadsInfo['http://filetodownload.exe']='Status: Download Started!';"
style="display:none"></iframe>
That may do the trick. But following IE's tradition, this could or could not work depending on the case...
If it does not work, some solutions that have proved useful include:
Put the onload handler in a function, and write in the definition of the iframe: onload="return theonloadfunction()" (even if the function does not return anything)
Instead of using the onload attribute, attach the event handler in javascript, like so:
iframe = document.getElementById("theiframeid")
iframe.attachEvent("onload", theonloadfunction);`
Note that attachEvent is for IE only. If you want to support other browsers you will have to detect it and use addEventListener for the non-IE cases.
Finally, you may try combinations of two or more of these solutions :)
<html>
<head>
<meta content = 'text/html;charset=utf-8' http-equiv = 'Content-Type'>
<meta content = 'utf-8' http-equiv = 'encoding'>
<script>
/*
First, I removed the setInterval(). Since you rely on the onload property we can aswell just check it on each onload.
Second, I changed your downloadsInfo to an object array.
Also be aware while testing, that some browsers cache your cancel/block choice and do not reask again for the same url.
Additionally firefox does not fire on frame downloads.
Furthermore the alert in your test might not show for overlapping or setting reasons.
*/
var downloadsInfo = [
{url: "http://download-installer.cdn.mozilla.net/pub/firefox/releases/26.0/win32/en-US/Firefox%20Setup%2026.0.exe", Status: "Connecting"},
{url: "http://download.piriform.com/ccsetup410.exe", Status: "Connecting"}
];
//IE has a problem in sometimes merely firing the onload propery once, which we bypass by dynamically creating them
//It is also less limited.
function iframeConnect(){
for(var i=0, j=downloadsInfo.length; i<j; i++){
var tF = document.createElement('iframe');
tF.arrayIndex = i; //For convenience
tF.style.display = 'none';
//Normal load event, working in ie8-11, chrome, safari
tF.onload = function(){
iframeExecuted(this.arrayIndex);
};
//Workaround for firefox, opera and some ie9
tF.addEventListener('DOMSubtreeModified', function(){
iframeExecuted(this.arrayIndex);
}, false);
document.body.appendChild(tF);
tF.src = downloadsInfo[i].url;
}
}
function iframeExecuted(i){
downloadsInfo[i].Status = 'Executed';
var tStatus = iframeFinished();
var tE = document.querySelector('h3');
if (tStatus.Done) tE.innerHTML = 'Finished'
else tE.innerHTML = 'Processed ' + tStatus.Processed + ' of ' + tStatus.Started;
}
function iframeFinished(){
for(var i=0, j=downloadsInfo.length; i<j; i++){
if (downloadsInfo[i].Status != 'Executed') break;
}
//Note that the Processed value is not accurate, yet it solves is testing purpose.
return {Done: (i == j), Processed: i, Started: j}
}
</script>
</head>
<body onload = 'iframeConnect()'>
<h3>Please wait for your downloads to start and do not reload this site.</h3>
</body>
</html>
I'm encountering a strange issue. I am developing a books application and using javascript onload. I read somewhere that its best to include your javascript at the end of the html. This works for most of the html loaded. However some complain that onload init() not found. This gets solved if i include the javascript in the html head. But than other htmls start behaving strangely. onload gets called before the page is fully loaded. i dont get the correct scroll width. Please suggest what could be worng. Whats the best way of including javascripts. Thanks
html is as follows
columizer id use css column-width which i've defined like this.
css style below
#columnizer
{
width:290px;
height:450px;
column-width:290px;
column-gap:10px;
word-wrap:break-word;
}
Javascript onload is defined like this.
function init()
{
docScrollWidth = document.getElementById('columnizer').scrollWidth;
document.getElementsByTagName('body')[0].style.width = docScrollWidth + "px";
window.external.notify(str);
}
Since the actual answer was in my comment, I'll add that to my answer:
My guess is that you're doing something like window.onload = init(); instead of window.onload = init; and the init function will have to be declared before you do that assignment. You assign function references without the parens. Using the parens causes it to get executed immediately.
You say you're using this code:
docScrollWidth = document.getElementsByTagName('body')[0].style.width
The main problem with this is that style.width ONLY reads a style attribute set directly on the body object. It doesn't get the width of the object as calculated by layout or CSS rules.
So, what you should use instead really depends upon what you're trying to do. The body width will nearly always be the same or more than the window width unless your content is entirely fixed width. So, that makes me wonder what you're trying to accomplish here? What you should use instead depends upon what you're really trying to do.
FYI, document.body is a direct reference to the body object so you don't need document.getElementsByTagName('body')[0].
First, let me define the problem. The window.onload event is used by programmers to kick-start their web applications. This could be something trivial like animating a menu or something complex like initialising a mail application. The problem is that the onload event fires after all page content has loaded (including images and other binary content). If your page includes lots of images then you may see a noticeable lag before the page becomes active. What we want is a way to determine when the DOM has fully loaded without waiting for all those pesky images to load also.
Mozilla provides an (undocumented) event tailor-made for this: DOMContentLoaded. The following code will do exactly what we want on Mozilla platforms:
// for Mozilla browsers
if (document.addEventListener) {
document.addEventListener("DOMContentLoaded", init, false);
}
So what about Internet Explorer?
IE supports a very handy (but non-standard) attribute for the tag: defer. The presence of this attribute will instruct IE to defer the loading of a script until after the DOM has loaded. This only works for external scripts however. Another important thing to note is that this attribute cannot be set using script. That means you cannot create a script using DOM methods and set the defer attribute – it will be ignored.
Using the handy defer attribute we can create a mini-script that calls our onload handler:
<script defer src="ie_onload.js" type="text/javascript"></script>
The contents of this external script would be a single line of code to call our onload event handler:
init();
There is a small problem with this approach. Other browsers will ignore the defer attribute and load the script immediately. There are several ways round this. My preferred method is to use conditional comments to hide the deferred script from other browsers:
<!--[if IE]><script defer src="ie_onload.js"></script><![endif]-->
IE also supports conditional compilation. The following code is the JavaScript equivalent of the above HTML:
// for Internet Explorer
/*#cc_on #*/
/*#if (#_win32)
document.write("<script defer src=ie_onload.js><\/script>");
/*#end #*/
So far so good? We now need to support the remaining browsers. We have only one choice – the standard window.onload event:
// for other browsers
window.onload = init;
There is one remaining problem (who said this would be easy?). Because we are trapping the onload event for the remaining browsers we will be calling the init function twice for IE and Mozilla. To get around this we should flag the function so that it is executed only once. So our init method will look something like this:
function init() {
// quit if this function has already been called
if (arguments.callee.done) return;
// flag this function so we don't do the same thing twice
arguments.callee.done = true;
// do stuff
};
I’ve provided a sample page that demonstrates this technique.
This is a basic question but google didn't provide any help.
I have a website and what to beable to run javascript on it.
In my directories I have index.html, and index.css. For the javascript file, I'm assuming it should be called index.js.
In my index.js file I have this:
var countTime = 0; // Number of seconds
var redirectURL = "http://example.com"; // URL to direct to
countTime = (countTime+1)*1000;
function updateCount(){
countTime = countTime-1000;
if(document.getElementById("countdownDisplay"))
document.getElementById("countdownDisplay").innerHTML = (countTime/1000);
if(countTime <= 0)
location.href = redirectURL;
else
setTimeout("updateCount()",1000);
}
updateCount();
However it's not working when I visit the page with a browser.
Do I have to do something in my html file like include index.js or something?
<script src="index.js" type="text/javascript"></script>
Should go in your <head>.
This will load the script for you and then the code gets executed.
Your also going to need something like
<div id="countdownDisplay"></div> in your <body> for the countdown to work.
Whilst I'm at it you probably want a
<style src="index.css" type="text/css"></style> in your <head> as well if you havn't already.
Yes, you need to include it in the HTML file. Here are some instructions.
basically when trying to write some html, you can either search on google how to write the code or as well search for a page which provides what you want to do and look into it's source. This way google would have helped you, because google uses javascript.
In addition, check your totalvalidator. It is a very useful firefox plugin for advanced html validation. It supports better evaluation than the w3c validator does.
It seems this is a known problem and has been asked several times before here in SO however I do not see anything specific to jQTouch so I thought I would give it a try.
jQT will dynamically load pages when a link is clicked. In this page I would like to include something like
<script>
$.include('javascriptfile.js', function() {alert('do something with results of this file to an already existing div element');};
</script>
The $.include is a jquery plugin I found that mimics the $.load with a few more smarts added to it. Tested to work on FF but not in Chrome or most importantly, Safari.
The alert is never displayed. FireBug never shows the javascript even being loaded. If I put an alert before the $.include I still do not see anything.
I have tried an onclick/ontap event that would then run this code that was included in the head tag, no luck.
Edit: I am using the r148 revision of jQT. This was working prior to moving to this version, i believe.
Did you try to add the javascript file using one of these two methods:
Static Way:
<script type="text/javascript">
function staticLoadScript(url){
document.write('<script src="', url, '" type="text/JavaScript"><\/script>');
}
staticLoadScript("javascriptfile.js");
modifyDivFn(processFnInFile());
</script>
Dynamic way:
<script type="text/javascript">
function dhtmlLoadScript(url){
var e = document.createElement("script");
e.src = url;
e.type="text/javascript";
document.getElementsByTagName("head")[0].appendChild(e);
}
onload = function(){
dhtmlLoadScript("javascriptfile.js");
modifyDivFn(processFnInFile());
}
</script>
After the include you can call a function that does the processing you want (that being processFnInFile()) which result will be passed to modifyDivFn (and modify the div you want.) You could do this in one function, just to illustrate the idea.
Source: Dynamically Loading Javascript Files
Well Geries, I appreciate your help but ultimately the answer required a drastic rethinking of how I was using JQTouch. The solution was to move everything to an onclick event and make all the hrefs link to #. This might be what you were talking about Geries.
In the onclick function I do the logic, preloading, loading of the page through my own GET through jquery, then use the public object jQT.goTo(div, transition). This seems to get around the WebKit bugs or whatever I was running into and this now owrks on FireFox, Chrome, Safari, iPhone, and the lot.
I do run into a few animation issues with JQT but I think these are known issues that I hope Stark and the gang at JQTouch are working on.
I want to give a minimal js code to random websites so that they can add a widget.
The code needs to run after the main page loads and include a parameter with the domain name. ( I don't want to hardcode it)
One option is to add this code just before the </body> (so It will run after the page loads):
<script type="text/javascript" id="widget_script">
document.getElementById('widget_script').src=location.protocol.toLowerCase()+"//mywebsite.com/?u="+encodeURIComponent(window.location.host);
</script>
This works in IE but not in Firefox. I see with Firebug that the src property is created correctly but the script from my site is not loaded.
My question is : what is the best way to do that ? (preferably by putting minimal lines on the header part.)
To further clarify the question: If I put a script on the header part, how do I make it run after it is loaded and the main page is loaded? If I use onload event in my script I may miss it because it may load after the onload event was fired.
You can try to statically include the script with document.write (is an older technique and not recommended to use as it can cause problems with more modern libraries):
var url = location.protocol.toLowerCase() +
"//mywebsite.com/?u="+encodeURIComponent(window.location.host);
document.write('<script src="', url, '" type="text/javascript"><\/script>');
Or with dynamically created DOM element:
var dynamicInclude = document.createElement("script");
dynamicInclude.src = url;
dynamicInclude.type = "text/javascript";
document.getElementsByTagName("head")[0].appendChild(dynamicInclude);
Later edit:
To ensure the script is run after onload this can be used:
var oldWindowOnload = window.onload;
window.onload = function() {
oldWindowOnload();
var url = location.protocol.toLowerCase() +
"//mywebsite.com/?u="+encodeURIComponent(window.location.host);
var dynamicInclude = document.createElement("script");
dynamicInclude.src = url;
dynamicInclude.type = "text/javascript";
document.getElementsByTagName("head")[0].appendChild(dynamicInclude);
}
I do not believe it can be shorter than this, apart from shorter variable names :)
Why not use the getScript method of jQuery to do the loading? If you don't want to be dependant on jQuery, you can trace through the source to learn how they tackled it.
Viewing a widely used library is always going to show you solutions to problems you didn't know you had. For example, you can see how jQuery manages to generate a callback when the script is loaded, and how it avoids a purported memory leak in IE.
You probably want to be implementing the non-blocking script technique. Essentially instead of modifying the src of a script, you're going to create and append a whole new script element.
Good write up here and there are standard ways to do this in YUI and jQuery. It's quite straightforward with only one gotcha which is well understood (and documented at that link).
Oh and this:
One option is to add this code just
before the </body> (so It will run
after the page loads):
...is not technically true: you're just making your script the last thing in the loading order.