Develop Reference

Distance measurement logic

Boy it was hard to give this problem a name...
I've been working on this "progress bar" logic, that when ever the user moves
his/her mouse - the indicator (in this case its progress bar) shows how close cursor is to the wanted object.
Basically it's like "hot 'n cold" kind of thing.
Here's the fiddle
...and this is the problem part
relativeDistance = ((maxMouseDistance - distance) / maxDistance);
if ((maxMouseDistance - distance) > maxDistance){
relativeDistance = 1- (((maxMouseDistance) / maxDistance) -1);
}
Since my code and distance measurements are based on trigonometry, it has a small problem: There's actually atleast two points on the screen, where the wanted distances are equal.
Try it and you'll notice what I mean.
Any ideas on how I could get rid of that...It's propably because of the logics, but I just don't see it.

Does this jsFiddle do what you want?
It uses the nearest corner to the mouse rather than the farthest corner. It will show 0% when the mouse is in any corner, and a positive percentage as the mouse approaches the target, even if the target is off-centre.
(function () {
var mX
, mY
, distance
, $distance = $('#distance')
, $element = $('#thetarget')
, maxMouseDistance
, relativeDistance;
var theWidth = $(document).width();
var theHeight = $(document).height();
$("#theWidth").text(theWidth);
$("#theHeight").text(theHeight);
function pythagoras(length, height) {
var length2 = length * length
, height2 = height * height
return Math.sqrt((length2 + height2));
}
/**/
var target = $("#thetarget");
target.css({
cursor: "default"
, border: "1px solid black"
, margin: 0});
var position = target.position(); // top left of target element
var tX = Math.floor(position.left)
var tY = Math.floor(position.top)
$("#targetPosition").text(tX + ":" + tY);
var corners = [
[0, 0]
, [theWidth, 0]
, [theWidth, theHeight]
, [0, theHeight]
]
function distanceToNearestCorner(x, y) {
var cornerX = x < tX ? 0 : theWidth
var cornerY = y < tY ? 0 : theHeight
return pythagoras(cornerX - tX, cornerY - tY)
}
/*Mouse movement tracking*/
$(document).mousemove(function (e) {
/*Get mouse coordinates*/
mX = e.pageX;
mY = e.pageY;
/*calculate distance between mouse and element*/
distance = pythagoras(tX - mX, tY - mY);
maxMouseDistance = distanceToNearestCorner(mX, mY)
relativeDistance = ((maxMouseDistance - distance) / maxMouseDistance);
$distance.text(distance);
var decimals = distance / 100;
var percents = 100 - (distance / 100);
$("#mouse").text(mX + ":" + mY);
//$("#distanceDecimals").text(decimals);
//$("#dFarCorner").text(maxDistance);
$("#md2FarCorner").text(maxMouseDistance);
$("#formula").text("(E to C max / M to C max) / (M to E distance/100)");
$("#theNumber").text(relativeDistance);
$('.fill').width((relativeDistance * 100) + "%");
});
})();
It doesn't update all the fields, but it does update the progress bar.
Original answer
You seem to have plenty of functions in there which are not being called.
Here's one that I have rewritten... but it doesn't get called:
function calculateDistance(elem, mouseX, mouseY) {
var deltaX = elem.offset().left - mouseX;
var deltaY = elem.offset().top - mouseY;
var delta2 = deltaX * deltaX + deltaY * deltaY;
var delta = Math.floor(Math.sqrt(delta2))
return delta
}
var elem = document.getElementById("targetPosition")
var relativeDistance = calculateDistance(elem , mX, mY)
In my implementation, elem is the HTML element that you consider to be the target. My function is an application of Pythagoras' theorem: it returns the square root of the sum of the distance from the target along the x and y axes, giving the length of the shortest line between the mouse and the target.
When I insert this into your jsFiddle, I see 0 appearing in the M2E Distance field when my cursor is just above the "T" of "Target".
Is this what you are looking for?

Your logic is correct. It's called a locus. http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/locirev1.shtml

Array value in randomly positioned div

Using this - random position of divs in javascript as a starting point I am trying to randomly position divs containing text from an array.
Current code (predominately copied Ken Redler's answer in the linked post):
(function makeDiv(){
var divsize = 200;
var color = '#'+ Math.round(0xffffff * Math.random()).toString(16);
//set up the array to hold the random div content
var boastsText = [];
var i = 0;
$(".boast ul li").each(function() { boastsText.push($(this).text()) });
$newdiv = $('<div/>').css({
'width':divsize+'px',
'height':divsize+'px',
'color': color
});
// make position sensitive to size and document's width
var posx = (Math.random() * ($(document).width() - divsize)).toFixed();
var posy = (Math.random() * ($(document).height() - divsize)).toFixed();
$newdiv.css({
'position':'absolute',
'left':posx+'px',
'top':posy+'px',
'display':'none'
}).html(boastsText[i]).appendTo( 'body' ).fadeIn(100).delay(1000).fadeOut(500, function(){
$(this).remove();
makeDiv();
});
})();
The only thing I have really added is the setting up of the array var boastsText = [] and the each function that populates that array.
The problem I have is I need to iterate over the array so each new div created uses the next item as it's content i.e. div 1 uses array item 0, div 2 uses item 1 etc... until it reaches the end of the array and then starts the process again.

I've modified your script a little bit to use a recursive function in order to iterate over the array and maintain the delay and fadeIn/Out you have:
(function() {
//set up the array to hold the random div content
var boastsText = [];
$(".boast ul li").each(function () {
boastsText.push($(this).text());
});
function makeDiv(i){
var divsize = 200;
var color = '#'+ Math.round(0xffffff * Math.random()).toString(16);
var $newdiv = $('<div/>').css({
'width':divsize+'px',
'height':divsize+'px',
'color': color
});
// make position sensitive to size and document's width
var posx = (Math.random() * ($(document).width() - divsize)).toFixed();
var posy = (Math.random() * ($(document).height() - divsize)).toFixed();
$newdiv.css({
'position':'absolute',
'left':posx+'px',
'top':posy+'px',
'display':'none'
}).html(boastsText[i]).appendTo('body').fadeIn(100).fadeOut(500, function() {
$(this).remove();
if (i === boastsText.length) return;
makeDiv(++i);
});
}
//Start the recursion
makeDiv(0);
}());

javascript (making collage from images)

javascript code for making collage through images working in mozilla but chrome
$(document).ready(function() {
var canvaswidth = $('.rc-contentholder').width();
var canvasheight = $('.rc-contentholder').height();
function setleftandtop(noofdivision) {
var elements = document.getElementsByClassName('rc-singlecontentholder');
var noofelements = elements.length;
//place the first row
currentelementid = elements[0].id;
$("#" + currentelementid).css('left', '0px');
$("#" + currentelementid).css('top', '0px');
for (j = 1; j < noofdivision; j++) {
previousleft = parseFloat(elements[j - 1].style.left);
top = 0;
previouswidth = parseFloat(elements[j - 1].style.width);
elements[j].style.left = (previousleft + previouswidth) + "px";
elements[j].style.top = 0;
}
//place the remaining rows
for (i = noofdivision; i < noofelements; i++) {
currentid = elements[i - noofdivision].id;
left = parseFloat(elements[i - noofdivision].style.left);
uppertop = parseFloat(elements[i - noofdivision].style.top);
console.log(uppertop)
height = $("#" + currentid).height();
console.log("id" + "=" + currentid + " " + "height" + "=" + ($("#" + currentid).height()));
elements[i].style.left = left + "px";
elements[i].style.top = (uppertop + height) + "px";
}
}
if (canvaswidth >= 1200) {
noofdivision = 5;
singlecontentholderwidth = canvaswidth / noofdivision;
$('.rc-singlecontentholder').css('width', singlecontentholderwidth);
setleftandtop(noofdivision);
} else if (canvaswidth >= 900) {
noofdivision = 4;
singlecontentholderwidth = canvaswidth / noofdivision;
$('.rc-singlecontentholder').css('width', singlecontentholderwidth);
setleftandtop(noofdivision);
} else if (canvaswidth >= 550) {
noofdivision = 3;
singlecontentholderwidth = canvaswidth / noofdivision;
$('.rc-singlecontentholder').css('width', singlecontentholderwidth);
setleftandtop(noofdivision);
} else if (canvaswidth >= 480) {
noofdivision = 2
singlecontentholderwidth = canvaswidth / noofdivision;
$('.rc-singlecontentholder').css('width', singlecontentholderwidth);
setleftandtop(noofdivision);
} else if (canvaswidth < 480) {
noofdivision = 1;
singlecontentholderwidth = canvaswidth / noofdivision;
$('.rc-singlecontentholder').css('width', singlecontentholderwidth);
setleftandtop(noofdivision);
}
});
in chrome the height of the division rc-singlecontentholder keeps changing dont know what is happening please help me. Help would be appreciated.

As a rule of thumb you should always provide a standalone example/snippet/jsfiddle, so it is easy for others to figure out exactly what your problem is. In your code the markup(HTML) is missing and several of your variables are not defined. However I will try to give you a push in the right direction from the information you have provided.
I deduced that you want to determine the amount of images your canvas can fit from an element with class 'rc-containerwidth'. The first thing I want to address is that if you iterate from
var j = 0
you can just use
elements[j]
but this is just a minor esthetic.
I am assuming that you have classes called 'rc-singlecontentholder' with actual content, that would make the divs have a width and a height. With this in mind the real problem I see with your code is that the first for loop sets the first n=(noofdivision-1) elements with class 'rc-singlecontentholder' to have top=0.
The second for loop starts at element number n=i-noofdivison. Since it starts at
var i = noofdivison;
this effectively starts at n=0, which means you are looping over the same elements as in the first loop. You then calculate the variable upperTop as the elements top position which will be 0.
upperTop = top = 0;
and finally sets the top of this element as top + height
elements[i].style.top = (upperTop + height) + 'px';
Which will cause the different elements to be positioned at the height of their container. This will happen to the first n=(noofdivison-1) elements and the rest will be placed depending on what your original css for these elements are, which are hard to guess from your question. These factors coupled together is likely what is causing the height in chrome to be different from the height of the divs in firefox. Hope this can point you in the right direction to bandage your code.
There are several improvements that can be done to the code apart from this, but this could be a good task to solve if you are in the stages of learning JavaScript.
If learning JavaScript is not of the essence then I suggest trying to reuse some of the libraries that already exists for image collages, which should be more robust and time-saving than creating your own.
You can check out one alternative called H5P Collage or check out how we used JavaScript to make it at github. Disclosure: I am one of the developers on the H5P team.

Generate numbers in side div at random position without overlapping

I want to display random numbers inside a div at random positions without overlapping.
I am able to display random number at random position but its going outside the box and overlapping each other.
Here is my code:
JS Fiddle
var width = $('.container').innerWidth();
var height = $('.container').innerHeight();
(function generate() { // vary size for fun
for (i = 0; i < 15; i++) {
var divsize = 12;
var color = '#' + Math.round(0xffffff * Math.random()).toString(16);
$newdiv = $('<div/>').css({
'width': divsize + 'px',
'height': divsize + 'px'
});
// make position sensitive to size and document's width
var posx = (Math.random() * (width - divsize)).toFixed();
var posy = (Math.random() * (height - divsize)).toFixed();
$newdiv.css({
'position': 'absolute',
'left': posx + 'px',
'top': posy + 'px',
'float': 'left'
}).appendTo('.container').html(Math.floor(Math.random() * 9));
}
})();
How can I do this?

You've got most of it figured out. You just need to think of the .container div as a grid to avoid any overlap or outlying items.
Just check out this fiddle.
Here's what the code looks like:
var tilesize = 18, tilecount = 15;
var gRows = Math.floor($(".container").innerWidth()/tilesize);
var gCols = Math.floor($('.container').innerHeight()/tilesize);
var vals = _.shuffle(_.range(tilecount));
var xpos = _.shuffle(_.range(gRows));
var ypos = _.shuffle(_.range(gCols));
_.each(vals, function(d,i){
var $newdiv = $('<div/>').addClass("tile");
$newdiv.css({
'position':'absolute',
'left':(xpos[i] * tilesize)+'px',
'top':(ypos[i] * tilesize)+'px'
}).appendTo( '.container' ).html(d);
});
PS:I have used underscore in my fiddle to make things easier for me and because I personally hate writing for loops.

If the number of divs you need to create is small enough (i.e. you're not risking that they won't fit) then a simple algorithm is:
pick a random position (x0, y0)-(x1, y1)
check if any previously selected rect overlaps
if none overlaps then add the rect, otherwise loop back and choose another random position
in code
var selected = [];
for (var i=0; i<num_divs; i++) {
while (true) {
var x0 = Math.floor(Math.random() * (width - sz));
var y0 = Math.floor(Math.random() * (height - sz));
var x1 = x0 + sz;
var y1 = y0 + sz;
var i = 0;
while (i < selected.length &&
(x0 >= selected[i].x1 ||
y0 >= selected[i].y1 ||
x1 <= selected[i].x0 ||
y1 <= selected[i].y0)) {
i++;
}
if (i == selected.length) {
// Spot is safe, add it to the selection
selected.push({x0:x0, y0:y0, x1:x1, y1:y1});
break;
}
// The choice collided with a previously added div
// just remain in the loop so a new attempt is done
}
}
In case the elements are many and it's possible to place n-1 of them so that there's no position where to put n-th element then things are a lot more complex.
For the solution of the 1-dimensional version of this problem see this answer.

You can add to array position of each number. And then when ou generate new position for digit you should check if posx posy in array, if false place number there, if true generate new posx and posy

Can I draw a line using jQuery?

I have a web app where I would like the user to draw a line in the following way: When he clicks on Point1 and he moves the mouse, draw the line from Point1 to the current mouse position and, when clicks to Point2 draw the final line from Point1 to Point2.
How can I do it using jQuery and/or one of its plugins?

Challenge accepted.
I tried to do it with CSS transforms and a bunch of Math in Javascript - after half an hour I have this:
http://jsfiddle.net/VnDrb/2/
Make 2 clicks into the gray square and a line should be drawn.
There is still a small bug that draws the line wrong when the angle is > 45 degree. Maybe someone else knows how to fix that. Maybe instead of using Math.asin (arcsinus), use a other trigonometrical function, but I'm really not good at it.
I thought I'd post it even there is a small bug, I think it's a good start for you.

I've tried a number of different approaches this weekend and the solution that worked best for me is from Adam Sanderson: http://monkeyandcrow.com/blog/drawing_lines_with_css3/
His demo is here: http://monkeyandcrow.com/samples/css_lines/
The core of it is very simple, which is always good.
div.line{
transform-origin: 0 100%;
height: 3px; /* Line width of 3 */
background: #000; /* Black fill */
}
function createLine(x1,y1, x2,y2){
var length = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
var angle = Math.atan2(y2 - y1, x2 - x1) * 180 / Math.PI;
var transform = 'rotate('+angle+'deg)';
var line = $('<div>')
.appendTo('#page')
.addClass('line')
.css({
'position': 'absolute',
'transform': transform
})
.width(length)
.offset({left: x1, top: y1});
return line;
}

You can not do it with jQuery and classic HTML.
You can do it using SVG (+svgweb for IE8- http://code.google.com/p/svgweb/ )
SVG can be dynamically created. jQuery + svgweb are working perfectly, you just need to know how to create SVG nodes and you need only jquerify this nodes. After jquerifiing in most cases used only one method attr()
You can do it using Raphael http://raphaeljs.com/ (based on SVG and VML)
You can do it using Canvas ( http://flashcanvas.net/ for IE8- )
For SVG programming will be this way:
Moment of creating first point: you create empty line var Line (also this points coordinates will be x1 and y1)
Then you bind on mousemove repaint of x2, y2 properties of Line
On mousedown after mousemove you freeze last line position.
UPDATE
You can do it with CSS/JS, but main problem is in calculations for IE8-, that has only Matrix filter for transformations.

Been using a modified version of this for a while now. Works well.
http://www.ofdream.com/code/css/xline2.php
So on first click, drop and object there as a placeholder div, maybe a little circle, then either keep redrawing a line as they move their mouse, or draw it when they click the second time, using the original placeholder as a guide.
I recently made another helper function for this, because my tool involves moving lines around:
function setLinePos(x1, y1, x2, y2, id) {
if (x2 < x1) {
var temp = x1;
x1 = x2;
x2 = temp;
temp = y1;
y1 = y2;
y2 = temp;
}
var line = $('#line' + id);
var length = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
line.css('width', length + "px");
var angle = Math.atan((y2 - y1) / (x2 - x1));
line.css('top', y1 + 0.5 * length * Math.sin(angle) + "px");
line.css('left', x1 - 0.5 * length * (1 - Math.cos(angle)) + "px");
line.css('-moz-transform', "rotate(" + angle + "rad)");
line.css('-webkit-transform', "rotate(" + angle + "rad)");
line.css('-o-transform', "rotate(" + angle + "rad)");
}
That is the jquery version, and in this iteration I have no IE requirement so I ignore it. I could be adapted from the original function pretty easily.

The class
function getXY(evt, element) {
var rect = element.getBoundingClientRect();
var scrollTop = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop;
var scrollLeft = document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft;
var elementLeft = rect.left + scrollLeft;
var elementTop = rect.top + scrollTop;
x = evt.pageX - elementLeft;
y = evt.pageY - elementTop;
return { x: x, y: y };
}
var LineDrawer = {
LineHTML: `<div style="cursor: pointer;transform-origin:center; position:absolute;width:200px;height:2px; background-color:blue"></div>`,
isDown: false,
pStart: {},
pCurrent :{},
containerID: "",
JLine: {},
angle: 0,
afterLineCallback: null,
Init: function (containerID, afterLineCallback) {
LineDrawer.containerID = containerID;
LineDrawer.afterLineCallback = afterLineCallback;
LineDrawer.JLine = $(LineDrawer.LineHTML).appendTo("#" + LineDrawer.containerID);
LineDrawer.JLine.css("transform-origin", "top left");
LineDrawer.JLine.hide();
//LineDrawer.JLine.draggable({ containment: "#" + LineDrawer.containerID });
$("#" + LineDrawer.containerID).mousedown(LineDrawer.LineDrawer_mousedown);
$("#" + LineDrawer.containerID).mousemove(LineDrawer.LineDrawer_mousemove);
$("#" + LineDrawer.containerID).mouseup(LineDrawer.LineDrawer_mouseup);
},
LineDrawer_mousedown: function (e) {
if (e.target === LineDrawer.JLine[0]) return false;
LineDrawer.isDown = true;
let p = LineDrawer.pStart = getXY(e, e.target);
LineDrawer.JLine.css({ "left": p.x, "top": p.y, "width": 1});
LineDrawer.JLine.show();
},
LineDrawer_mousemove: function (e) {
if (!LineDrawer.isDown) return;
LineDrawer.pCurrent = getXY(e, document.getElementById("jim"));
let w = Math.sqrt(((LineDrawer.pStart.x - LineDrawer.pCurrent.x) * (LineDrawer.pStart.x - LineDrawer.pCurrent.x)) + ((LineDrawer.pStart.y - LineDrawer.pCurrent.y) * (LineDrawer.pStart.y - LineDrawer.pCurrent.y)));
LineDrawer.JLine.css("width", w - 2);
LineDrawer.angle = Math.atan2((LineDrawer.pStart.y - LineDrawer.pCurrent.y), (LineDrawer.pStart.x - LineDrawer.pCurrent.x)) * (180.0 / Math.PI);
//the below ensures that angle moves from 0 to -360
if (LineDrawer.angle < 0) {
LineDrawer.angle *= -1;
LineDrawer.angle += 180;
}
else LineDrawer.angle = 180 - LineDrawer.angle;
LineDrawer.angle *= -1;
LineDrawer.JLine.css("transform", "rotate(" + LineDrawer.angle + "deg");
},
LineDrawer_mouseup: function (e) {
LineDrawer.isDown = false;
if (LineDrawer.afterLineCallback == null || LineDrawer.afterLineCallback == undefined) return;
LineDrawer.afterLine(LineDrawer.angle, LineDrawer.pStart, LineDrawer.pCurrent);
},
};
Usage:
var ECApp = {
start_action: function () {
LineDrawer.Init("jim", ECApp.afterLine);
},
afterLine(angle, pStart, pEnd) {
//$("#angle").text("angle : " + angle);
let disp = "angle = " + angle;
disp += " Start = " + JSON.stringify(pStart) + " End = " + JSON.stringify(pEnd);
//alert(disp);
$("#angle").text("angle : " + disp);
}
}
$(document).ready(ECApp.start_action);
HTML
<div class="row">
<div class="col">
<div id="jim" style="position:relative;width:1200px;height:800px;background-color:lightblue;">
</div>
</div>