The type of positioning is really affecting my JavaScript
I'm currently making a drag-and-drop JavaScript engine. I'm currently making a "bounding" feature, so that the drag-object is bounded by a container with the class .bound
. When I make the drag-object, I also find out if it has bounds:
function makeObj(e) {
obj = new Object();
obj.element = e;
obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;
obj.posX = event.clientX - e.offsetLeft;
obj.posY = event.clientY - e.offsetTop;
var curleft = curtop = 0;
if (e.offsetParent) {
do {
curleft += e.offsetLeft;
curtop += e.offsetTop;
//alert(e.id + ":" + e.innerHTML);
if(~e.className.search(/bound/)) {
obj.boundX = curleft - obj.element.offsetLeft;
obj.boundY = curtop - obj.element.offsetTop;
return obj;
}
} while (e = e.offsetParent);
}
return obj;
}
My loops work, however setting the bounds does not.
I would like this html to affect the function:
<div id="center" class="bound">
<h1>Hello World! <hr /></h1>
<div id="box" class="bound">
<p class="drag square" id="one"> One </p>
<p class="drag square" id="two"> Two </p>
</div>
</div>
As much as this html:
<div id="center"> <!-- Difference is here -->
<h1>Hello World! <hr /></h1>
<div id="box" class="bound">
<p class="drag square" id="one"> One </p>
<p class="drag square" id="two"> Two </p>
</div>
</div>
The difference is the .bound
class, which has position: relative
set.
Here is the CSS:
@charset "utf-8";
/* CSS Document */
* {
padding: 0px;
margin: 0px;
}
.drag {
position: absolute;
-webkit-user-select: none;
-moz-user-select: none;
user-select: none;
}
.bound {
position: relative;
}
.square {
width: 100px;
height: 100px;
background: red;
cursor:move;
}
#center {
width: 500px;
height: 300px;
margin: auto;
margin-top: 50px;
background-color:#ccc;
text-align: center;
border-radius: 25px;
-moz-border-radius: 25px;
}
#box {
background-color: #FF3;
height: 278px;
border-radius: 0 0 25px 25px;
-moz-border-radius: 0 0 25px 25px;
opacity: 0.5;
}
How do I make it so the position:
attribute doesn't affect how the engine works- So that any position will work. Absolute, Relative, Static, ect? How can I make my .drag
objects have any kind of positioning besides absolute?
I will post the entire engine below (and a jsfiddle link) just in case it is useful:
http://jsfiddle.net/Upvdm/1/
开发者_StackOverflow社区// JavaScript Document
var dragObj;
document.addEventListener("mousedown", down, false);
function down(event) {
if(~event.target.className.search(/drag/)) {
dragObj = makeObj(event.target);
dragObj.element.style.zIndex="100";
document.addEventListener("mousemove", freeMovement, false);
}
}
function freeMovement(event) {
if (typeof(dragObj.element.mouseup) == "undefined")
document.addEventListener("mouseup", drop, false);
//Prevents redundantly adding the same event handler repeatedly
dragObj.element.style.left = Math.max(0, Math.min(event.clientX - dragObj.posX, dragObj.boundX)) + "px";
dragObj.element.style.top = Math.max(0, Math.min(event.clientY - dragObj.posY, dragObj.boundY)) + "px";
}
function drop() {
dragObj.element.style.zIndex="1";
document.removeEventListener("mousemove", freeMovement, false);
document.removeEventListener("mouseup", drop, false);
//alert("DEBUG_DROP");
}
function makeBoundlessObj(e) {
obj = new Object();
obj.element = e;
obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;
obj.posX = event.clientX - e.offsetLeft;
obj.posY = event.clientY - e.offsetTop;
return obj;
}
function makeObj(e) {
obj = new Object();
obj.element = e;
obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;
obj.posX = event.clientX - e.offsetLeft;
obj.posY = event.clientY - e.offsetTop;
var curleft = curtop = 0;
if (e.offsetParent) {
do {
curleft += e.offsetLeft;
curtop += e.offsetTop;
//alert(e.id + ":" + e.innerHTML);
if(~e.className.search(/bound/)) {
obj.boundX = curleft - obj.element.offsetLeft;
obj.boundY = curtop - obj.element.offsetTop;
return obj;
}
} while (e = e.offsetParent);
}
return obj;
}
function findPos(obj) { // Donated by `lwburk` on StackOverflow
var curleft = curtop = 0;
if (obj.offsetParent) {
do {
curleft += obj.offsetLeft;
curtop += obj.offsetTop;
} while (obj = obj.offsetParent);
return { x: curleft, y: curtop };
}
}
Thank you so much for reading and helping!
while (e = e.offsetParent);
Should be
while (e == e.offsetParent); //alternatively, use ===
In C-like languages (like JavaScript), = means "Put the value of the variable on the right to the variable on the left." However, == means "Do the values on both sides match?"
JavaScript considers anything but a few things (like 0, an empty string, null and undefined) as false and everything else as true. So, the expression e = e.offsetParent
will always return true.
Tested it and it works on the JSFiddle example you sent.
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