Prevent/stop auto anchor link from occurring - javascript

I need to prevent the automatic scroll-to behavior in the browser when using link.html#idX and <div id="idX"/>.
The problem I am trying to solve is where I'm trying to do a custom scroll-to functionality on page load by detecting the anchor in the url, but so far have not been able to prevent the automatic scrolling functionality (specifically in Firefox).
Any ideas? I have tried preventDefault() on the $(window).load() handler, which did not seem to work.
Let me reiterate this is for links that are not clicked within the page that scrolls; it is for links that scroll on page load. Think of clicking on a link from another website with an #anchor in the link. What prevents that autoscroll to the id?
Everyone understand I'm not looking for a workaround; I need to know if (and how) it's possible to prevent autoscrolling to #anchors on page load.
NOTE
This isn't really an answer to the question, just a simple race-condition-style kluge.
Use jQuery's scrollTo plugin to scroll back to the top of the page, then reanimate the scroll using something custom. If the browser/computer is quick enough, there's no "flash" on the page.
I feel dirty just suggesting this...
$(document).ready(function(){
// fix the url#id scrollto "effect" (that can't be
// aborted apparently in FF), by scrolling back
// to the top of the page.
$.scrollTo('body',0);
otherAnimateStuffHappensNow();
});
Credit goes to wombleton for pointing it out. Thanks!

This seems the only option I can see with ids:
$(document).ready(function() {
$.scrollTo('0px');
});
It doesn't automatically scroll to classes.
So if you identify your divs with unique classes you will lose a bit of speed with looking up elements but gain the behaviour you're after.
(Thanks, by the way, for pointing out the scroll-to-id feature! Never knew it existed.)
EDIT:

I know this is an old thread but i found something without the need to scroll. Run this first before any other scripts. It puts an anchor before the first element on the page that prevents the scroll because it is on top of the page.
function getAnchor(sUrl)
{
if( typeof sUrl == 'string' )
{
var i = sUrl.indexOf( '#' );
if( i >= 0 )
{ return sUrl.substr( i+1 ).replace(/ /g, ''); }
}
return '';
};
var s = getAnchor(window.location.href);
if( s.length > 0 )
{ $('<a name="'+s+'"/>').insertBefore($('body').first()); }
Cheers!
Erwin Haantjes

Scroll first to top (fast, no effects pls), and then call your scroll function. (I know its not so pretty)
or just use a prefix

This worked well for me:
1- put this on your css file
a[name] { position: absolute; top: 0px }
2- put this on your document.ready bind right before you start animating (if you're animating at all)
$("a[name]").css("position","relative");
Might need tweaking depending on your stylesheet/code but you get the idea.
Credit to: http://cssbeauty.com/skillshare/discussion/1882/disable-anchor-jump/

Related

How to dynamically change the height of an empty div using Javascript onclick and restore with onScroll

Context: I have a button on the top of the page in the header, and I want visitors to jump to the form section which is at a lower position on the same page. For some unchangeable factors, the form is partially hidden under the header after page jump, so I am thinking of creating a new div before the form and change the height of the div to push the form down after jumping. Then, when users scroll again on the page, the height should go back to 0.
Problem: When I click on the DemoButton for the first time, the div height doesn't change and the form goes under header, but the second time it works. I don't know how to fix that.
The basic html structure is shown as following:
<div>
<a href="#demoForm" id="DemoButton">
<button>request demo</button>
</a>
</div>
<div id="space"></div>
<from id="demoForm">...</form>
JavaScript:
window.onload = function comparison() {
window.addEventListener("scroll", reset, false);
var demo = document.getElementById('DemoButton');
demo.onclick = uniform;
}
function reset() {
document.getElementById('Space').style.height = '0';
}
function uniform() {
document.getElementById('Space').style.height = '160px';
};
I know a lot of people are using newer CSS for reactive headers these days. I believe it's done using media queries, and I might suggest researching it some more. (I have some experience, it was very easy and cool too.)
Ideally, you'd want something like this to happen in CSS without JavaScript at all. See if you can get it figured out that way.
Using very light Javascript, it seems the easiest thing to do would be to just offset the scroll by the height of the header once the button has been clicked. You can hard-code the header height or calculate it dynamically.
So...
;;;;;;;;;;;;;;
; $ = document ;
; id = 'getElementById' ;
;;;;;;;;;;;;;
onload = function (e)
{
$[id]('DemoButton')
. onclick = function offset(e)
{
document.body.scrollTop -= $[id]('Header').offsetHeight;
}
;
}
Notes
You may have to wrap it in a 5ms setTimeout. Easy enough.
I don't remember all the cross-browseryness. There might be a need to parseInt or use document.documentElement. But at least you don't have cross-browser scroll events to deal with now, so this should be nice.

jQuery syntax added var

I needed a jQuery function to fix my div when the page is scrolled.
I found this:
var fixed = false;
var topTrigger = $('#sticker').offset().top;
$(document).scroll(function() {
if( $(this).scrollTop() >= topTrigger ) {
if( !fixed ) {
fixed = true;
$('#sticker').css({'position':'fixed', 'top':'0'});
}
} else {
if( fixed ) {
fixed = false;
$('#sticker').css({'position':'relative'});
}
}
});
Now, since I'm not a super beginner with jQuery, I tried to skim it and understand it. The only things I don't understand are the things related to the var:fixed. I tried to delete the var and the if statement related to that and the function works perfectly.
My question : why is that variable there, what does it mean, what feature does it add to the entire function?
Why should I keep it there instead of deleting everything related to that variable?
The scroll event will be fired multiple times as the user scrolls. If you keep on changing the DOM attributes, then the performance of the site may slow down.
To avoid applying the style multiple times, they are having a flag called fixed. So once the user has scrolled a particular height, they will trigger change the DOM to be fixed. Later they need not again change the CSS style.
Only if the user scrolls back less than the threshold they need to change the style again.

How can I scroll to a page element in jQuery Mobile?

I have a long jQuery mobile page and would like to scroll to an element halfway down this page after the page loads.
So far I've tried a few things, the most successful being:
jQuery(document).bind("mobileinit", function() {
var target;
// if there's an element with id 'current_user'
if ($("#current_user").length > 0) {
// find this element's offset position
target = $("#current_user").get(0).offsetTop;
// scroll the page to that position
return $.mobile.silentScroll(target);
}
});
This works but then the page position is reset when the DOM is fully loaded. Can anyone suggest a better approach?
Thanks
A bit late, but I think I have a reliable solution with no need for setTimeout(). After a quick look into the code, it seems that JQM 1.2.0 issues a silentScroll(0) on window.load for chromeless viewport on iOS. See jquery.mobile-1.2.0.js, line 9145:
// window load event
// hide iOS browser chrome on load
$window.load( $.mobile.silentScroll );
What happens is that this conflicts with applicative calls to silentScroll(). Called too early, the framework scrolls back to top. Called too late, the UI flashes.
The solution is to bind a one-shot handler to the 'silentscroll' event that calls window.scrollTo() directly (silentScroll() is little more than an asynchronous window.scrollTo() anyway). That way, we capture the first JQM-issued silentScroll(0) and scroll to our position immediately.
For example, here is the code I use for deep linking to named elements (be sure to disable ajax load on inbound links with data-ajax="false"). Known anchor names are #unread and #p<ID>. The header is fixed and uses the #header ID.
$(document).bind('pageshow',function(e) {
var $anchor;
console.log("location.hash="+location.hash);
if (location.hash == "#unread" || location.hash.substr(0,2) == "#p") {
// Use anchor name as ID for the element to scroll to.
$anchor = $(location.hash);
}
if ($anchor) {
// Get y pos of anchor element.
var pos = $anchor.offset().top;
// Our header is fixed so offset pos by height.
pos -= $('#header').outerHeight();
// Don't use silentScroll() as it interferes with the automatic
// silentScroll(0) call done by JQM on page load. Instead, register
// a one-shot 'silentscroll' handler that performs a plain
// window.scrollTo() afterward.
$(document).bind('silentscroll',function(e,data) {
$(this).unbind(e);
window.scrollTo(0, pos);
});
}
});
No more UI flashes, and it seems to work reliably.
The event you're looking for is "pageshow".
I was digging a lot this issue, also at jQuery mobile official forum.
Currently it seems that there is no solution (at least for me).
I tried different events (mobileinit, pageshow) and different functions (silentscroll, scrolltop) as suggested above, but, as a result, I always have page scrolled until all images and html is finished loading, when page is scrolled to top again!
Partial and not really efficient solution is using a timer as suggested in comment to sgliser's answer; unfortunately with a timeout is difficult to know when page will be fully loaded and if scroll happened before that, it will scroll back to top at the end of load, while if it happens too long after page has fully loaded, the user is already scrolling page manually, and further automated scroll will create confusion.
Additionally, would be useful to have silentscroll or other function to address a specific id or class and not plain pixels, because with different browsers, resolutions and devices it may give different and not correct positioning of the scroll.
Hope someone will find a smarter and more efficient solution than this.

How does one disable Caching in jQuery Mobile UI

Tried...
<div data-role="page" data-cache="30">
<div data-role="page" data-cache="never">
<div data-role="page" data-cache="false">
<div data-role="page" cache="false">
Nothing seemes to work... so at the moment I'm fixing the problem on the server-side via...
.'?x='.rand()
.'&x='.rand()
I don't want to disable the AJAX just the caching. There has to be a better way though... am I missing something?
Thanks,
Serhiy
Thank you for the answers guys, and even though they didn't quite work for me they did point me in the direction to find the code I was looking for.
This is the code that I found on this gentleman's Github Gist.
https://gist.github.com/921920
jQuery('div').live('pagehide', function(event, ui){
var page = jQuery(event.target);
if(page.attr('data-cache') == 'never'){
page.remove();
};
});
There is also a back button code in that Gist, but I don't seem to need it really as my back button seems to work just fine...
Page caching is now off by default in jQM RC1. See the extract below from the jQM website about page caching: http://jquerymobile.com/demos/1.0rc1/docs/pages/page-cache.html
If you prefer, you can tell jQuery Mobile to keep previously-visited pages in the DOM instead of removing them. This lets you cache pages so that they're available instantly if the user returns to them.
To keep all previously-visited pages in the DOM, set the domCache option on the page plugin to true, like this:
$.mobile.page.prototype.options.domCache = true;
Alternatively, to cache just a particular page, you can add the data-dom-cache="true" attribute to the page's container:
<div data-role="page" id="cacheMe" data-dom-cache="true">
You can also cache a page programmatically like this:
pageContainerElement.page({ domCache: true });
The drawback of DOM caching is that the DOM can get very large, resulting in slowdowns and memory issues on some devices. If you enable DOM caching, take care to manage the DOM yourself and test thoroughly on a range of devices.
Have you tried to overwrite the default value ?
$(document).bind("mobileinit", function(){
$.mobile.page.prototype.options.domCache = false;
});
This works for me
Method 1
This disables AJAX
Read
http://jquerymobile.com/demos/1.0a2/#docs/api/globalconfig.html
Set ajaxLinksEnabled to false and it will not load and cache those pages, just work as normal links.
Method 2
Second idea is to remove cached elements. You can bind to pagehide event and make it remove the page instead. If not present in DOM, the page will be loaded again.
It can be done with this code as a proof of concept:
$('.ui-page').live('pagehide',function(){ $(this).remove(); });
But it needs a little work. The above code breaks the history. It prooves that you will only be able to use it with pages you intend to be leaves in your sitemap tree. Therefore you have to create a special selector for them or bind it to only certain pages.
Also you can bind to a button's click or mousedown event, get its href, generate page id out of it and find the div by id to remove it before jqm tries to look for it.
I have found no advised way of disabling the cache or forcing loading.
Martin's answer should be the right one in my opinion but jQuery Mobile cache the first page no matter what. https://github.com/jquery/jquery-mobile/issues/3249
I've opted to "patch" the behaviour of $.mobile.page.prototype.options.domCache = false and data-dom-cache="true"
$(document).on('pagehide', function (e) {
var page = $(e.target);
if (!$.mobile.page.prototype.options.domCache
&& (!page.attr('data-dom-cache')
|| page.attr('data-dom-cache') == "false")
) {
page.remove();
}
});
Here's my working solution:
$('.selector').live( 'pagebeforecreate', function () {
$.mobile.urlHistory.stack = [];
$.mobile.urlstack = [];
$( '.ui-page' ).not( '.ui-page-active' ).remove();
});
I wrote an (original in German) article about that topic, maybe that helps.
Link to google translated article

How to disable user's input while loading page with jQuery?

I have a heavy-jquerized page with some links, various user inputs and such.
I use jquery, with actions defined in a
$(document).ready( function() {
....
} );
block.
But while the page is loading (or, even worse - reloading), and a user clicks a link, the href action from it is triggered, as the javascript isn't loaded / active yet.
I wanted to block it somehow. One way that came to my mind is to put a transparent div over whole document, that would receive the click events instead of the layer below it. Then, in my .ready function in javascript, I could hide that div making it possible to use the page.
Is it a good practice? Or should I try some different approach?
Another option is to use the jQuery BlockUI plugin (which probably usew the same or similar idea behind the scenes).
If you don't want your links to act like links (ie their href is never meant to followed), why make them links in the first place? You'd be better served by making your clickable elements a div or span (something without a default action), and attaching the click handler as per normal.
I'd really advise against blocking the ui with a div - it seems the entirely wrong approach, making the page non-functional to someone with JS disabled, as well as blocking other common tasks like copying text.
In light of the clarification, to block the UI only if JS is enabled, but not yet loaded, I'd suggest the following.
HTML (first thing after body):
<script type="text/javascript">document.write('<div id="UIBlocker">Please wait while we load...</div>')</script>
CSS:
#UIBlocker
{
position: fixed; /* or absolute, for IE6 */
top: 0;
bottom: 0;
left: 0;
right: 0;
}
Or, if you prefer not to use document.write, leave the UIBlocker div as straight HTML at the top of body, but have the following in head
HTML:
<noscript>
<style type="text/css">
#UIBlocker { display: none !important; }
</style>
</noscript>
This will ensure it does not block for non-JS enabled browsers
A transparent div could work, assuming it’s positioned above everything. (I’m never quite clear how visible an element has to be to receive click events.)
You might want to make the div visible though; it could be equally confusing for visitors if they can see everything on the page, but not click it.
You’ll probably need to use JavaScript to make the div as tall as the page though.
The overlay DIV should work. Another option would be to place all the content inside a hidden container visibility: hidden then toggle to visible as the last $(document).ready statement.
As you said it yourself javascript isn't loaded yet. Maybe the css isn't loaded either.
so something with visual element will not work i think. IF you want to do some with the viaual elements (css) you have to hardcode it in the html node <tagname style="blabla">
You could possibly add the href behavious in a later stadium when the js is loaded.
What you get is a <span> with a title and this should set the behaviour or something. I used a title, but can be a different attribute.
This doesn't use any jquery, only for loading
$(document).reade(function () {
relNoFollow();
});
function relNoFollow() {
var FakeLinks = document.getElementsByTagName('span');
if( FakeLinks.length > 0 ) {
for( var i = 0; i < FakeLinks.length; i++ ) {
if( FakeLinks[i].title.indexOf( 'http://' ) != -1 ) {
FakeLinks[i].onmouseout = fakelinkMouseOut;
FakeLinks[i].onmouseover = fakelinkMouseOver;
FakeLinks[i].onclick = fakelinkClick;
}
}
}
}
function fakelinkMouseOver() {
this.className = 'fakelink-hover';
}
function fakelinkMouseOut() {
this.className = 'fakelink';
}
function fakelinkClick() {
window.location.href = this.title;
}

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