Develop Reference

Circle moving out of window

var circle = document.getElementById("circle");
function moveUp() {
var top = circle.offsetTop;
newTop = top - 10;
circle.style.top = newTop + "px";
console.log("moveUP Called")
}
function moveDown() {
var top = circle.offsetTop;
newTop = top + 10;
circle.style.top = newTop + "px";
console.log("moveDown Called")
}
function moveLeft() {
var left = circle.offsetLeft;
newLeft = left - 10;
circle.style.left = newLeft + "px";
console.log("moveLeft Called")
}
function moveRight() {
var left = circle.offsetLeft;
newLeft = left + 10;
circle.style.left = newLeft + "px";
console.log("moveRight Called")
}
window.addEventListener("keypress", (event) => {
if (event.key == 'w') {
moveUp();
} else if (event.key == 's') {
moveDown();
} else if (event.key == 'a') {
moveLeft();
} else if (event.key == 'd') {
moveRight();
}
})
body {
margin: 2px;
background-color: aquamarine;
}
#circle {
height: 100px;
width: 100px;
background-color: blue;
border-radius: 50%;
position: absolute;
}
In the above code where on key press circle moves, for example on 'w' it moves up, for 's' it moves down and so on.
But the problem is that the circle even moves out of the window, how do I fix it and what is the problem??

var circle = document.getElementById("circle");
console.log(window.innerWidth, window.innerHeight)
function moveUp() {
var top = circle.offsetTop;
console.log(top)
newTop = top - 10;
if(newTop < 0) {
newTop = 0;
}
circle.style.top = newTop + "px";
}
function moveDown() {
var top = circle.offsetTop;
var height = circle.offsetHeight + top;
if((height + 10) >= window.innerHeight) {
return;
}
newTop = top + 10;
circle.style.top = newTop + "px";
/* console.log("moveDown Called") */
}
function moveLeft() {
var left = circle.offsetLeft;
newLeft = left - 10;
if(newLeft<0) {
newLeft = 0;
}
circle.style.left = newLeft + "px";
}
function moveRight() {
var left = circle.offsetLeft;
newLeft = left + 10;
if(newLeft > window.innerWidth - 100 ) {
newLeft = window.innerWidth - 100 ;
}
circle.style.left = newLeft + "px";
}
window.addEventListener("keypress", (event) => {
if (event.key == 'w') {
moveUp();
} else if (event.key == 's') {
moveDown();
} else if (event.key == 'a') {
moveLeft();
} else if (event.key == 'd') {
moveRight();
}
})
body{
margin:2px;
background-color: aquamarine;
}
#circle{
height: 100px;
width: 100px;
background-color: blue;
border-radius: 50%;
position: absolute;
overflow: hidden;
}
<div id="circle">
</div>
Explaination
for moveup() if the position is a negative number that means the div is going out of the viewport. So with the if condition new position will be always set to 0 preventing the div to go negative position.
for moveDown() first you get the offsetTop which means how far is the box from top position along with the offsetHeight which represents the height of the box. So add these two to get the total height. Now simply check if this height is going over the innerHeight + the distance(10) you are going with each move. If it is more than the innerHeight simply return. otherwise move the box.
moveLeft() is same as moveUp().
moveRight() is also same as moveDown() but here we're calculating the innerWidth. Subtract it with the box width so it doesn't go outside the viewport. Now simple condition check and set the new right position.
hope it helped

What is the problem?
There is no problem. CSS does exactly what you told it to do.
For example, you can click on 'w' couple of times, which will set left property for your absolutely positioned circle to, let's say, -160px. This will instruct the browser to move your element to the left, away from the viewport, i.e. to position it -160px of the left edge of the initial containing block or nearest positioned ancestor. More about left property: https://developer.mozilla.org/en-US/docs/Web/CSS/left
I would not say that it is a problem, because it is exactly what left is used for - move elements to whatever position you like. Sometimes you can hide elements by setting their position: absolute; left: -10000px;
How do I fix it?
If you don't want your circle to move away from the viewport, you need to check if your circle is 'touching' the viewport. I will use example with the left, but the same logic can be applied to top, right and bottom.
So for the left, this will consist of two parts:
Check what is the initial distance from your circle to the left edge of the viewport.
Check if absolute value of your new left value is not greater than this distance.
For example, for the left method:
var elDistanceToLeft = window.pageXOffset + circle.getBoundingClientRect().left;
function moveLeft() {
let left = circle.offsetLeft;
newLeft = Math.abs(left - 10) <= elDistanceToLeft ? left - 10 : -elDistanceToLeft;
circle.style.left = newLeft + "px";
}
In this case your circle will move all way to the left (on pressing 'a') until it 'touches' the viewport (screen). Then it will stop.
Here is a code snippet
var elDistanceToLeft = window.pageXOffset + circle.getBoundingClientRect().left
function moveLeft() {
let left = circle.offsetLeft;
newLeft = Math.abs(left - 10) <= elDistanceToLeft ? left - 10 : -elDistanceToLeft;
circle.style.left = newLeft + "px";
}
window.addEventListener("keypress", (ev) => { if (ev.key == 'a') { moveLeft();} })
#circle {
height: 100px;
width: 100px;
background-color: blue;
border-radius: 50%;
position: absolute;
}
#parent {
position: relative;
padding: 200px;
}
<div id="parent">
<div id="circle"></div>
</div>

XY coords following cursor movements

i am looking to have this cursor effect on the body:
https://www.screenshot-magazine.com/
i do have two separate codes, one for the bloc following the mouse and another to get the xy coords.
But i am too beginner to merge both together or make both work in parallel to have the XY coods printed in the box following my cursor moves.
Someone could help me?
Thanks a lot in advance:)
Anto
here the two codes:
1-bloc following mouse movements
<style>
#divtoshow {
position:absolute;
display:none;
color: #C0C0C0;
background-color: none;
}
<script type="text/javascript">
var divName = 'divtoshow'; // div that is to follow the mouse (must be position:absolute)
var offX = 15; // X offset from mouse position
var offY = 15; // Y offset from mouse position
function mouseX(evt) {if (!evt) evt = window.event; if (evt.pageX) return evt.pageX; else if (evt.clientX)return evt.clientX + (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft); else return 0;}
function mouseY(evt) {if (!evt) evt = window.event; if (evt.pageY) return evt.pageY; else if (evt.clientY)return evt.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop); else return 0;}
function follow(evt) {
var obj = document.getElementById(divName).style;
obj.left = (parseInt(mouseX(evt))+offX) + 'px';
obj.top = (parseInt(mouseY(evt))+offY) + 'px';
}
document.onmousemove = follow;
</script>
<body>
<div id='onme' onMouseover='document.getElementById(divName).style.display="block"' onMouseout='document.getElementById(divName).style.display="none"'>
<div id="divtoshow">test</div>
2-get XY coords on body
<script>
function readMouseMove(e){
var result_x = document.getElementById('x_result');
var result_y = document.getElementById('y_result');
result_x.innerHTML = e.clientX;
result_y.innerHTML = e.clientY;
}
document.onmousemove = readMouseMove;
</script>
</head>
<body>
<h2 id="x_result">0</h2>
<h2 id="y_result">0</h3>
</body>

Your CSS is fine. You could have moved #x-result and #y-result into #divtoshow, and then set the left and right in readMouseMove. I've modified your code a bit. I'll explain it on the way
const xResult = document.getElementById("x-result");
const yResult = document.getElementById("y-result");
const divToShow = document.getElementById("divtoshow");
document.onmousemove = function (e) {
let mouse = {
x: e.clientX, // this is 2018, so you can just directly use clientX
y: e.clientY // and clientY
};
divToShow.style.left = `${mouse.x + 16}px`; // add a padding so that the text is not rendered directly below the mouse
divToShow.style.top = `${mouse.y + 16}px`;
xResult.innerHTML = `X: ${mouse.x}`; // write the text into the output divs
yResult.innerHTML = `Y: ${mouse.y}`;
};
#divtoshow {
color: #C0C0C0;
position: absolute;
}
<div id="divtoshow">
<span id="x-result">X: 0</span> <br> // i changed the h2s to spans because h2s have HUGE text
<span id="y-result">Y: 0</span>
</div>
You can add the #onme integration by yourself.

Creating a Windows 8 Explorer simulation - mouse selection issue

As a little practice I decided to recreate the Windows 8 Explorer file list panel, and all went well, until I wanted to add the mouse selection. It's basically the feature that allows you to select multiple files by dragging your mouse along the window, drawing a square, which should select all "files" that fall under it.
The only problem I have is that I can't seem to find a way to add the selected class to the elements under the selection
Here's the related code: (full code available in a working fiddle)
<ul class="files">
<li>
<span class="icon folder"></span>
<span class="name">Folder</span>
</li>
</ul>
.selection {
position: absolute;
border: 1px solid #39F;
background-color: rgba(51,153,255,.4);
display: none;
}
$(function(){
var $body = $(document.body);
var selecting = false,
$selectionDiv = $(document.createElement('div')).addClass('selection').appendTo($body),
startX, startY;
$body.on({
mousedown: function(e){
if (e.target === document.body){
e.stopPropagation();
startX = e.clientX;
startY = e.clientY;
selecting = true;
$selectionDiv.show().css({top:startY+'px',left:startX+'px',width:'0px',height:'0px'});
}
},
mousemove: function(e){
if (selecting){
var currentX = e.clientX,
currentY = e.clientY;
var subX = currentX - startX,
subY = currentY - startY;
if (subX < 0){
subX *= -1;
$selectionDiv.css('left',startX+(currentX-startX));
}
else $selectionDiv.css('left',startX+'px');
if (subY < 0){
subY *= -1;
$selectionDiv.css('top',startY+(currentY-startY));
}
else $selectionDiv.css('top',startY+'px');
$selectionDiv.css({
width: subX,
height: subY,
});
}
}
}).on('mouseup blur mouseleave',function(){
if (selecting){
$selectionDiv.hide();
selecting = false;
}
});
});

If I understand you correctly, you need to determine which elements are contained inside the selection box. Here's the code which seems to do the job (it's supposed to go into your mousemove event handler):
var topLeftX = Math.min(startX, currentX),
topLeftY = Math.min(startY, currentY),
bottomRightX = Math.max(startX, currentX),
bottomRightY = Math.max(startY, currentY);
$('.files li').each(function() {
var offset = $(this).offset(),
width = $(this).outerWidth(),
height = $(this).outerHeight();
if (offset.left < bottomRightX
&& offset.left + width > topLeftX
&& offset.top < bottomRightY
&& offset.top + height > topLeftY) {
$(this).addClass('selected');
}
else {
$(this).removeClass('selected');
}
});
This code goes through all the elements of your file list and runs rectangle overlap test (the algorithm for which I got from this answer) for the selection box and the list element. Usage of outerWidth() and outerHeight() makes sure that the border is also taken into consideration.
I also noticed that when you release the mouse your handler which resets the selection gets called:
$(window).click(function(){
$('.files li').removeClass('selected');
})
As a possible solution, you can move this into your mousedown handler.
Here's JSFIddle which works for me in Chrome 35: http://jsfiddle.net/5Hzm4/2/

zooming a selected part of image with cursor event

I have this jsfiddle : http://jsfiddle.net/seekpunk/JDU9f/1/
what I want is when the user do a selection the selected part is zoomed in .Is there anyway to achieve this ?
this is the code so far :
var canvas = document.getElementById("MyCanvas");
var ctx = canvas.getContext('2d'),
w = canvas.width,
h = canvas.height,
x1,
y1,
isDown = false;
var img = new Image();
img.src = "http://www.stockfreeimages.com/static/homepage/female-chaffinch-free-stock-photo-106202.jpg";
canvas.onmousedown = function (e) {
var rect = canvas.getBoundingClientRect();
x1 = e.clientX - rect.left;
y1 = e.clientY - rect.top;
isDown = true;
}
canvas.onmouseup = function () {
isDown = false;
}
canvas.onmousemove = function (e) {
if (!isDown) return;
var rect = canvas.getBoundingClientRect(),
x2 = e.clientX - rect.left,
y2 = e.clientY - rect.top;
ctx.clearRect(0, 0, w, h);
ctx.drawImage(img, 0, 0, w, h);
ctx.strokeRect(x1, y1, x2 - x1, y2 - y1);
}
img.onload = function () {
ctx.drawImage(img, 0, 0, w, h);
};
I can make the selection but how can i zoom the selected part only ? like this example : http://canvasjs.com/docs/charts/basics-of-creating-html5-chart/zooming-panning/

For those looking for zooming functionality without the use of a canvas, here's a pretty foolproof solution using a simple <img />:
$(window).on("load",function() {
//VARS===================================================
var zoom = {
zoomboxLeft:null, zoomboxTop:null, //zoombox
cursorStartX:null, cursorStartY:null, //cursor
imgStartLeft:null, imgStartTop:null, //image
minDragLeft:null,maxDragLeft:null, minDragTop:null,maxDragTop:null
};
//KEY-HANDLERS===========================================
$(document).keydown(function(e) {
if (e.which==32) {e.preventDefault(); if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").addClass("drag");}} //SPACE
});
$(document).keyup(function(e) {
if (e.which==32) {if (!$(".zoombox img").hasClass("moving")) {$(".zoombox img").removeClass("drag");}} //SPACE
});
//RESET IMAGE SIZE=======================================
$(".reset").on("click",function() {
var zoombox = "#"+$(this).parent().attr("id")+" .zoombox";
$(zoombox+" img").css({"left":0, "top":0, "width":$(zoombox).width(), "height":$(zoombox).height()});
}).click();
//ZOOM&DRAG-EVENTS=======================================
//MOUSEDOWN----------------------------------------------
$(".zoombox img").mousedown(function(e) {
e.preventDefault();
$(".zoombox img").addClass("moving");
var selector = $(this).next();
var zoombox = $(this).parent();
$(zoombox).addClass("active");
//store zoombox left&top
zoom.zoomboxLeft = $(zoombox).offset().left + parseInt($(zoombox).css("border-left-width").replace(/\D+/,""));
zoom.zoomboxTop = $(zoombox).offset().top + parseInt($(zoombox).css("border-top-width").replace(/\D+/,""));
//store starting positions of cursor (relative to zoombox)
zoom.cursorStartX = e.pageX - zoom.zoomboxLeft;
zoom.cursorStartY = e.pageY - zoom.zoomboxTop;
if ($(".zoombox img").hasClass("drag")) {
//store starting positions of image (relative to zoombox)
zoom.imgStartLeft = $(this).position().left;
zoom.imgStartTop = $(this).position().top;
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = $(zoombox).width() - $(this).width();
zoom.maxDragLeft = 0;
zoom.minDragTop = $(zoombox).height() - $(this).height();
zoom.maxDragTop = 0;
} else {
//set drag boundaries (relative to zoombox)
zoom.minDragLeft = 0;
zoom.maxDragLeft = $(zoombox).width();
zoom.minDragTop = 0;
zoom.maxDragTop = $(zoombox).height();
//activate zoom-selector
$(selector).css({"display":"block", "width":0, "height":0, "left":zoom.cursorStartX, "top":zoom.cursorStartY});
}
});
//MOUSEMOVE----------------------------------------------
$(document).mousemove(function(e) {
if ($(".zoombox img").hasClass("moving")) {
if ($(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
//update image position (relative to zoombox)
$(img).css({
"left": zoom.imgStartLeft + (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX,
"top": zoom.imgStartTop + (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY
});
//prevent dragging in prohibited areas (relative to zoombox)
if ($(img).position().left <= zoom.minDragLeft) {$(img).css("left",zoom.minDragLeft);} else
if ($(img).position().left >= zoom.maxDragLeft) {$(img).css("left",zoom.maxDragLeft);}
if ($(img).position().top <= zoom.minDragTop) {$(img).css("top",zoom.minDragTop);} else
if ($(img).position().top >= zoom.maxDragTop) {$(img).css("top",zoom.maxDragTop);}
} else {
//calculate selector width and height (relative to zoombox)
var width = (e.pageX-zoom.zoomboxLeft)-zoom.cursorStartX;
var height = (e.pageY-zoom.zoomboxTop)-zoom.cursorStartY;
//prevent dragging in prohibited areas (relative to zoombox)
if (e.pageX-zoom.zoomboxLeft <= zoom.minDragLeft) {width = zoom.minDragLeft - zoom.cursorStartX;} else
if (e.pageX-zoom.zoomboxLeft >= zoom.maxDragLeft) {width = zoom.maxDragLeft - zoom.cursorStartX;}
if (e.pageY-zoom.zoomboxTop <= zoom.minDragTop) {height = zoom.minDragTop - zoom.cursorStartY;} else
if (e.pageY-zoom.zoomboxTop >= zoom.maxDragTop) {height = zoom.maxDragTop - zoom.cursorStartY;}
//update zoom-selector
var selector = $(".zoombox.active .selector")[0];
$(selector).css({"width":Math.abs(width), "height":Math.abs(height)});
if (width<0) {$(selector).css("left",zoom.cursorStartX-Math.abs(width));}
if (height<0) {$(selector).css("top",zoom.cursorStartY-Math.abs(height));}
}
}
});
//MOUSEUP------------------------------------------------
$(document).mouseup(function() {
if ($(".zoombox img").hasClass("moving")) {
if (!$(".zoombox img").hasClass("drag")) {
var img = $(".zoombox.active img")[0];
var selector = $(".zoombox.active .selector")[0];
if ($(selector).width()>0 && $(selector).height()>0) {
//resize zoom-selector and image
var magnification = ($(selector).width()<$(selector).height() ? $(selector).parent().width()/$(selector).width() : $(selector).parent().height()/$(selector).height()); //go for the highest magnification
var hFactor = $(img).width() / ($(selector).position().left-$(img).position().left);
var vFactor = $(img).height() / ($(selector).position().top-$(img).position().top);
$(selector).css({"width":$(selector).width()*magnification, "height":$(selector).height()*magnification});
$(img).css({"width":$(img).width()*magnification, "height":$(img).height()*magnification});
//correct for misalignment during magnification, caused by size-factor
$(img).css({
"left": $(selector).position().left - ($(img).width()/hFactor),
"top": $(selector).position().top - ($(img).height()/vFactor)
});
//reposition zoom-selector and image (relative to zoombox)
var selectorLeft = ($(selector).parent().width()/2) - ($(selector).width()/2);
var selectorTop = ($(selector).parent().height()/2) - ($(selector).height()/2);
var selectorDeltaLeft = selectorLeft - $(selector).position().left;
var selectorDeltaTop = selectorTop - $(selector).position().top;
$(selector).css({"left":selectorLeft, "top":selectorTop});
$(img).css({"left":"+="+selectorDeltaLeft, "top":"+="+selectorDeltaTop});
}
//deactivate zoom-selector
$(selector).css({"display":"none", "width":0, "height":0, "left":0, "top":0});
} else {$(".zoombox img").removeClass("drag");}
$(".zoombox img").removeClass("moving");
$(".zoombox.active").removeClass("active");
}
});
});
/*CONTAINER-------------------*/
#container {
width: 234px;
height: 199px;
margin-left: auto;
margin-right: auto;
}
/*ZOOMBOX=====================*/
/*IMAGE-----------------------*/
.zoombox {
position:relative;
width: 100%;
height: 100%;
border: 2px solid #AAAAAA;
background-color: #666666;
overflow: hidden;
}
.zoombox img {position:relative;}
.zoombox img.drag {cursor:move;}
.zoombox .selector {
display: none;
position: absolute;
border: 1px solid #999999;
background-color: rgba(255,255,255, 0.3);
}
/*CONTROL---------------------*/
.reset {float:left;}
.info {float:right;}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="container">
<!--ZOOMBOX-->
<div class="zoombox">
<img src="http://www.w3schools.com/colors/img_colormap.gif" />
<div class="selector"></div>
</div>
<input type="button" class="reset" value="Reset" /><span class="info">Press SPACE to drag</span>
</div>
jsfiddle: http://jsfiddle.net/2nt8k8e6/
The container element can be anything, just place the .zoombox on your webpage and it should work.
You should even be able to put multiple .zoomboxes next to each other in the same container-element. I haven't tested it though.
It's not too complicated, there's not a whole lot of comments, but the variable names are pretty self-explanatory and make the code easy enough to read, and all the jquery-functions can be looked up.
The code is essentially divided into three handlers: .mousedown(), .mousemove(), .mouseup().
- In mousedown some values are stored into variables (like the start-coordinates for the selector), which are used in mousemove and mouseup as a reference.
If you want to know exactly what's happening, just have a look at the code, as I said it's not too difficult.

mousedown div containment to parent(latest)

My inner div is suppose to move around with the mouse cursor on mousemove but i want it to stop at the if statement if it is dragging with the isDragging variable so it will drag smoothly but it seems to not stop any suggestion and help would be appreciated
update: jsFiddle
var yellow = $('#yellow');
var offset = yellow.offset();
var offsetWidth = offset.left + yellow.width();
var offsetHeight = offset.top + yellow.height();
var isDragging = false;
var red = $('#red');
$('#red').hide();
yellow.on('mousedown', function(event) {
$('#red').show();
});
yellow.on('mouseup', function(event) {
$('#red').hide();
});
yellow.on('mousemove', function (e) {
if(e.pageX > offset.left + ($(red).width() / 2) && e.pageX < offsetWidth - ($(red).width() / 2)
&& e.pageY > offset.top + ($(red).height() / 2) && e.pageY < offsetHeight - ($(red).height() / 2) && !isDragging ){
red.css("left", e.pageX - $(red).width() / 2 );
red.css("top", e.pageY - $(red).height() / 2);
}
$('#red').draggable(
{'containment':'#yellow',
start:function(event, ui) {
isDragging = true;
},
drag:function(event, ui) {
isDragging = true;
},stop:function(event, ui) {
isDragging = false;
}
});
});
<div id="yellow">
<div id="red"></div>
</div>
#yellow {
position: absolute;
width: 250px;
height: 250px;
background-color: Yellow;
}
#red {
position: absolute;
width: 100px;
height: 100px;
background-color: red;
z-index: 100;
}

I can't say i am proud of this solution but it seems to get the stuff done:
http://jsfiddle.net/pPn3v/42/
var yellow = $('#yellow');
var offset = yellow.offset();
var offsetWidth = offset.left + yellow.width();
var offsetHeight = offset.top + yellow.height();
var red = $('#red');
yellow.on('mousemove', function (e) {
if(e.pageX+red.width() < offsetWidth
&& e.pageY+red.height() < offsetHeight){
red.css("left", e.pageX);
red.css("top", e.pageY);
}
});
red.on('mousemove', function (e) {
if(e.pageX+red.width() < offsetWidth
&& e.pageY+red.height() < offsetHeight){
red.css("left", e.pageX);
red.css("top", e.pageY);
}
});