How to find the offset client position of an element using Javascript? (I assume the same code can be written in a BHO or Gecko/NPAPI).
The problem I am facing is a way to find out the offset client position of the element. The e.srcElement.offsetX/Y does not give the correct value always (same goes for clientX/Y). In some cases we also need to consider the parent element scroll.
How do we do this in general? Is there an easy way for this?
See the code below:
function getOffsetSum(elem) {
var top=0, left=0;
while(elem) {
top = top + parseInt(elem.offsetTop);
left = left + parseInt(elem.offsetLeft);
elem = elem.offsetParent;
}
return {top: top, left: left};
}
function getElementTop ( Elem )
{
var elem;
if ( document.getElementById )
{
elem = document.getElementById ( Elem );
}
else if ( document.all )
{
elem = document.all[Elem];
}
yPos = elem.offsetTop;
tempEl = elem.offsetParent;
while ( tempEl != null )
{
yPos += tempEl.offsetTop;
tempEl = tempEl.offsetParent;
}
return yPos;
}
function getElementLeft ( Elem )
{
var elem;
if ( document.getElementById )
{
var elem = document.getElementById ( Elem );
}
else if ( document.all )
{
var elem = document.all[Elem];
}
xPos = elem.offsetLeft;
tempEl = elem.offsetParent;
while ( tempEl != null )
{
xPos += tempEl.offsetLeft;
tempEl = tempEl.offsetParent;
}
return xPos;
}
Pass the element id to the functions.
To include scrolling, take a look at this jQuery event listener to log the scrollTop and the offset.
// Don't put this in the scroll event listener callback, or that will be unnecessarily performance intensive.
var offset = $("#id").offset().top;
$(window).bind("scroll", function() {
console.log(
$(window).scrollTop() +
offset
);
});
To get the offset alone,
("#id").offset().top;
CoffeeScript version of Orhun Alp Oral's answer:
getOffset = (elem)->
top = 0
left = 0
while elem
top += parseInt(elem.offsetTop)
left += parseInt(elem.offsetLeft)
elem = elem.offsetParent
{top, left}
Related
I was looking for a function that would scroll a given element into view with some smart behavior:
if an element is descendant of a scrollable element - that ancestor is scrolled rather than body.
if an element is descendant of a positioned element - body won't be scrolled.
I didn't find any suitable function, so I made one and wanted some expert opinion on it. Please check the plunkr http://plnkr.co/edit/DNGWLh5cH1Cr1coZbwpa?p=preview . There are problems with animated scroll in FF, so please use Chrome to check the logic.
To illustrate, what I'm looking for - here is the first update that came to mind - if we reached an element that can scroll, lets call it SC (Scroll Parent), we should not only scroll SC to make the target visible inside it, but also recursively scroll SC itself into view, since it may outside of the currently visible are of the page. Here is the update plunkr http://plnkr.co/edit/DNGWLh5cH1Cr1coZbwpa?p=preview (also applied fix for FF scrolling problem).
And here is the code of the function
function scrollTo(target){
//Position delta is used for scrollable elements other than BODY
var combinedPositionDelta = 0;
var previousParent = $(target);
var parent = $(target).parent();
while(parent){
combinedPositionDelta += previousParent.position().top - parent.position().top;
//If we reached body
if(parent.prop("tagName").toUpperCase() == "BODY"){
scrollBody(target.offset().top);
break;
}
//if we reached an element that can scroll
if(parent[0].scrollHeight > parent.outerHeight()){
scrollElementByDelta(parent,combinedPositionDelta);
//Recursively scroll parent into view, since it itself might not be visible
scrollTo(parent);
break;
}
//if we reached a apositioned element - break
if(parent.css('position').toUpperCase() != 'STATIC'){
console.log("Stopping due to positioned parent " + parent[0].outerHTML);
break;
}
previousParent = parent;
parent = parent.parent();
}
}
var offsetSkin = 20;
function scrollElementByDelta(element,offsetDelta){
$(element).animate({
scrollTop: element.scrollTop() + (offsetDelta - offsetSkin)
}, 1000);
}
function scrollBody(offset){
$('body,html').animate({
scrollTop: offset - offsetSkin
}, 1000);
}
Well I'm Using this one which works very well for me:
function scrollIntoView (element, alignTop) {
var document = element.ownerDocument;
var origin = element, originRect = origin.getBoundingClientRect();
var hasScroll = false;
var documentScroll = this.getDocumentScrollElement(document);
while (element) {
if (element == document.body) {
element = documentScroll;
} else {
element = element.parentNode;
}
if (element) {
var hasScrollbar = (!element.clientHeight) ? false : element.scrollHeight > element.clientHeight;
if (!hasScrollbar) {
if (element == documentScroll) {
element = null;
}
continue;
}
var rects;
if (element == documentScroll) {
rects = {
left : 0,
top : 0
};
} else {
rects = element.getBoundingClientRect();
}
// check that elementRect is in rects
var deltaLeft = originRect.left - (rects.left + (parseInt(element.style.borderLeftWidth, 10) | 0));
var deltaRight = originRect.right
- (rects.left + element.clientWidth + (parseInt(element.style.borderLeftWidth, 10) | 0));
var deltaTop = originRect.top - (rects.top + (parseInt(element.style.borderTopWidth, 10) | 0));
var deltaBottom = originRect.bottom
- (rects.top + element.clientHeight + (parseInt(element.style.borderTopWidth, 10) | 0));
// adjust display depending on deltas
if (deltaLeft < 0) {
element.scrollLeft += deltaLeft;
} else if (deltaRight > 0) {
element.scrollLeft += deltaRight;
}
if (alignTop === true && !hasScroll) {
element.scrollTop += deltaTop;
} else if (alignTop === false && !hasScroll) {
element.scrollTop += deltaBottom;
} else {
if (deltaTop < 0) {
element.scrollTop += deltaTop;
} else if (deltaBottom > 0) {
element.scrollTop += deltaBottom;
}
}
if (element == documentScroll) {
element = null;
} else {
// readjust element position after scrolls, and check if vertical scroll has changed.
// this is required to perform only one alignment
var nextRect = origin.getBoundingClientRect();
if (nextRect.top != originRect.top) {
hasScroll = true;
}
originRect = nextRect;
}
}
}
}
I hope this helps.
If you do not mind venturing into jQuery, the scrollTo plugin is the best bet. It handles most needs and gives a very refined smooth trasition.
Hope it helps.
I'm trying to workout the height of an iFrame and can not understand why
document.body.offsetHeight + document.body.bottomMargin
does not equal
document.documentElement.offsetHeight
when all other margins are set to zero and the bottom margin has a value below 16px.
Once the bottom margin is more than 16px the above two values equal each other in FireFox and are within 1px in Chrome.
Strangely this problem doesn't effect the width calculation.
After much digging around I came up with this to solve the problem.
function getIFrameHeight(){
function getComputedBodyStyle(prop) {
return parseInt(
document.defaultView.getComputedStyle(document.body, null),
10
);
}
return document.body.offsetHeight +
getComputedBodyStyle('marginTop') +
getComputedBodyStyle('marginBottom');
}
and an expanded version for IE8 and below.
function getIFrameHeight(){
function getComputedBodyStyle(prop) {
function getPixelValue(value) {
var PIXEL = /^\d+(px)?$/i;
if (PIXEL.test(value)) {
return parseInt(value,base);
}
var
style = el.style.left,
runtimeStyle = el.runtimeStyle.left;
el.runtimeStyle.left = el.currentStyle.left;
el.style.left = value || 0;
value = el.style.pixelLeft;
el.style.left = style;
el.runtimeStyle.left = runtimeStyle;
return value;
}
var
el = document.body,
retVal = 0;
if (document.defaultView && document.defaultView.getComputedStyle) {
retVal = document.defaultView.getComputedStyle(el, null)[prop];
} else {//IE8 & below
retVal = getPixelValue(el.currentStyle[prop]);
}
return parseInt(retVal,10);
}
return document.body.offsetHeight +
getComputedBodyStyle('marginTop') +
getComputedBodyStyle('marginBottom');
}
function yHandler () {
var show = document.getElementById('show');
var contentHeight = show.offsetHeight;
var yOffset = show.pageYOffset;
var y = yOffset + show.innerHeight;
if(y >= contentHeight) {
alert("ok")
}
}
show.onscroll = yHandler;
how to check if the scrollbar has reached the end of div?
Some code for you to work on:
var scroll = document.getElementById('scroll');
var content = document.getElementById('content');
scroll.onscroll = function(){
var total = scroll.scrollTop + scroll.clientHeight;
if(total == content.clientHeight)
alert('Reached bottom!');
}
http://jsfiddle.net/EY6qP/
Thor's method works perfectly well (+1), but you could also rely on scrollHeight.
(function(scroll){
scroll.onscroll = function(){
if (scroll.scrollTop + scroll.clientHeight == scroll.scrollHeight) {
console.log('hither!');
}
}
})(document.getElementById('scroll'));
Use scrollHeight, scrollTop and clientHeight attributes to detect the scroll bar reached bottom end or not.
function handleScroll() {
var div = document.getElementById("div-id");
if(Math.abs(Math.round(div.scrollHeight - div.scrollTop) - div.clientHeight) > 3) {
console.log("Scroll bar reached bottom end");
return true;
}
return false;
};
I have 3 pictures cropped by span.main{overflow:hidden}. User can pan the span with touch events and explore the hidden parts of the picture.
Code so far:
document.addEventListener('DOMContentLoaded', function() {
var box = document.querySelector('.main');
box.addEventListener("touchstart", onStart, false);
box.addEventListener("touchmove", onMove, false);
box.addEventListener("touchend", onEnd, false);
});
var startOffsetX, startOffsetY;
var moving = false;
function getPos(ev) {
return {
x: ev.touches ? ev.touches[0].clientX : ev.clientX,
y: ev.touches ? ev.touches[0].clientY : ev.clientY
};
}
function onStart(ev) {
moving = true;
var box = document.querySelector('.main');// I need something like $(this)
var pos = getPos(ev);
startOffsetX = pos.x + box.scrollLeft;
startOffsetY = pos.y + box.scrollTop;
if (ev.preventDefault)
ev.preventDefault();
else
ev.returnValue = false;
}
function onMove(ev) {
if (moving) {
var pos = getPos(ev);
var x = startOffsetX - pos.x;
var y = startOffsetY - pos.y;
var box = document.querySelector('.main'); // I need something like $(this)
box.scrollLeft = x;
box.scrollTop = y;
if (ev.preventDefault)
ev.preventDefault();
else
ev.returnValue = false;
}
}
function onEnd(ev) {
if (moving) {
moving = false;
}
}
The problem is that only the first thumbnail works as expected. I've tried:
-querySelector only returns the first element so if I add ID's and querySelector('#box1,#box2,#box3') should work. Nein. I thing I have a 'this' problem on the functions...
-Place events (as Apple suggests) inline <div class="box" onStart="ontouchstartCallback( ev);" ontouchend="onEnd( ev );"ontouchmove="onMove( ev );" > <img></div> looked like a solution yet...My guess, because of 'this' again...
You want to use the querySelectorAll method instead. It returns all matched elements in the subtree instead of only the first one (which is what querySelector does). Then loop through them using a for loop.
var elements = document.querySelectorAll('.main');
for (var i = 0, ii = elements.length; i < ii; ++i) {
var element = elements[i];
element.ontouchstart = onStart;
// ...
}
The other approach you can take (and it is probably a better one) is to use event delegation and set the event listeners on a parent element and decide which of the pictures is being manipulated by checking the target property of each event.
<div id="pictures">
<span class="main"><img /></span>
<span class="main"><img /></span>
<span class="main"><img /></span>
</div>
var parent = document.getElementById('pictures');
parent.ontouchstart = function (e) {
var box = e.target.parentNode; // parentNode because e.target is an Image
if (box.className !== 'main') return;
onStart(e, box);
};
I have some javascript that should move my div element every 400 milliseconds. From debugging I have found that all my code works except when I go to move the div element. Ie, this code:
block.style.left = xPos[index] + "px";
I am unsure why this code doesn't move my div? Should I use a different method (other than object.style.top etc.) to move my div?
My java script:
<script LANGUAGE="JavaScript" type = "text/javascript">
<!--
var block = null;
var clockStep = null;
var index = 0;
var maxIndex = 6;
var x = 0;
var y = 0;
var timerInterval = 400; // milliseconds
var xPos = null;
var yPos = null;
function moveBlock()
{
//alert( index ); // if you use this you will see my setInterval works fine
if ( index < 0 || index >= maxIndex || block === null || clockStep === null )
{
clearInterval( clockStep );
clockStep = null;
return;
}
block.innerHTML = "yellow"; // this works (just a debug test) so I know block points to the correct HTML element
block.style.left = xPos[index] + "px"; // this doesn't work
block.style.top = yPos[index] + "px";
index++;
}
function onBlockClick( blockID )
{
if ( clockStep !== null )
{
return;
}
block = document.getElementById( blockID );
index = 0;
x = parseInt( block.style.left, 10 );
y = parseInt( block.style.top, 10 );
xPos = new Array( x+10, x+20, x+30, x+40, x+50, x+60 );
yPos = new Array( y-10, y-20, y-30, y-40, y-50, y-60 );
clockStep = setInterval( "moveBlock()", timerInterval );
}
-->
</script>
The value of block.style.left and block.style.top is not set unless you use an absolutely-positioned div with preset values for both left and top (in fact, your array is filled with NaN when I tested). For instance, the code works fine with a div defined like this:
<div id="div1" style="position:absolute;left:100px;top:100px;
width:150px;height:150px;background-color:yellow;"
onclick="onBlockClick(this.id);">
HI
</div>