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Make a multiple objects with javascript and png

I'm trying to get a spaceship animation scene with a group of comets going down.
//Create a comet div with img attached to it
var cometScene = function(spaceNo){
var b = document.createElement('div');
b.id = 'cometio';
var cometImage = document.createElement('img');
cometImage.setAttribute('src', 'images/comet1.png');
b.appendChild(cometImage);
document.getElementById('wrap').appendChild(b);
}
//Comet move
function cometMove(){
var comet = document.getElementById('cometio');
var pos = 0;
var interval = setInterval(scene, 3);
function scene(){
if (pos === 1000){
clearInterval(interval);
} else {
pos++;
comet.style.top = pos + 'px';
comet.style.left = pos + 'px';
}
}
setInterval(scene, 3)
}
But when I call a function cometScene(3) I'm not getting 3 similar objects. Also how these objects can be allocated across the whole screen as this is just a single div.
function main(){
var w = document.createElement('div');
w.id = 'wrap';
document.querySelector('body').appendChild(w);
astronautScene();
cometScene();
shaceshipScene();
cometMove();
astronautMove();
}

This it what I would do:
Give the comets a class instead of an id, because there can be more of them.
Because there can be multiple use a loop to iterate through them
To give them the ability to move freely, they need to have position:absolute or something similiar
Don't use the same variable for the position of all comets, because they could be in different positions
To get the current position just parse the currect top and left value to a Number
//Create a comet div with img attached to it
var cometScene = function(spaceNo) {
var b = document.createElement('div');
b.className = 'cometio';
var cometImage = document.createElement('img');
cometImage.setAttribute('src', 'images/comet1.png');
b.appendChild(cometImage);
document.getElementById('wrap').appendChild(b);
}
//Comet move
function cometMove() {
var comets = document.getElementsByClassName('cometio');
for (let i = 0; i < comets.length; i++) {
const comet = comets[i];
comet.style.top = "0px";
comet.style.left = "0px";
comet.style.position = "absolute";
var interval = setInterval(scene, 3);
function scene() {
let x = parseInt(comet.style.left);
let y = parseInt(comet.style.top);
if (x === 1000) {
clearInterval(interval);
} else {
comet.style.top = (1 + x) + 'px';
comet.style.left = (1 + y) + 'px';
}
}
}
//setInterval(scene, 3)don't start the interval twice
}
function main() {
var w = document.createElement('div');
w.id = 'wrap';
document.querySelector('body').appendChild(w);
//astronautScene();
cometScene();
//shaceshipScene();
cometMove();
//astronautMove();
}
main();

Snap.svg Drag while Zoomed

When I use drag() on a scaled (zoomed) object, the object moves according to the scale, so that if for example, the scale is set to 3 -- then each 1px move of the mouse is multiplied by 3.
After 20 or so pixel moves by the mouse the behavior is completely unacceptable.
Is that a bug or am I doing something wrong?
var g = s.g();
g.transform("scale(3)");
var rect = g.rect(20,20,40,40);
var circle = g.circle(60,150,50);
var move = function(dx,dy) {
this.attr({
transform: this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [dx, dy]
});
}
var start = function() {
this.data('origTransform', this.transform().local );
}
var stop = function() {
console.log('finished dragging');
}
rect.drag(move, start, stop );
circle.drag(move, start, stop );
See fiddle at http://jsfiddle.net/mje8knLf/1/ (just drag one of the shapes)
TIA!

To do this, we need to account for existing transformations that appear on all the outer elements.
Here is a plugin I did a while back to help with this.
The main bit is the dragMove function. We find the existing other transforms that are applied (there are 3 types of transform matrix in Snap on an element, localMatrix, diffMatrix, globalMatix), and invert it to get the matrix that we will want to apply to allow for the existing effect. (If there are some cases where diffMatrix doesn't work, take a look at globalMatrix).
Then using that, we can use y() and x() on the new drag amount, to find what it would be in the new coordinate space.
Snap.plugin( function( Snap, Element, Paper, global ) {
Element.prototype.altDrag = function() {
this.drag( dragMove, dragStart, dragEnd );
return this;
}
var dragStart = function ( x,y,ev ) {
this.data('ot', this.transform().local );
}
var dragMove = function(dx, dy, ev, x, y) {
var tdx, tdy;
var snapInvMatrix = this.transform().diffMatrix.invert();
snapInvMatrix.e = snapInvMatrix.f = 0;
tdx = snapInvMatrix.x( dx,dy ); tdy = snapInvMatrix.y( dx,dy );
this.transform( "t" + [ tdx, tdy ] + this.data('ot') );
}
var dragEnd = function() {
}
});

Try: transform: this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [dx/3, dy/3].
Basic implementation:-
Scale is a global variable (can be a FLOAT also)
All dx and dy motion is divided by Scale
sidenote: all elements can be dragged out of the box. You might want to implement some movement limit around the edges.

Here I am using svg-pan-zoom.js for the pan and zoom for SVG, very easy to use.
And I am using snap.svg
var svgElement;
var panZoomPlan;
function setPanZoom(){
svgElement = document.querySelector('svg');
panZoomPlan = svgPanZoom(svgElement);
panZoomPlan.setMinZoom(0.1);
panZoomPlan.setMaxZoom(50);
panZoomPlan.setZoomScaleSensitivity(0.2);
panZoomPlan.disableDblClickZoom();
}
function set_draggable(svg_element) {
var shape = plan.select("#" + svg_element);
shape.drag(dragNode, dragStart, dragStop);
}
var dragStart = function() {
panZoomPlan.disablePan();
panZoomPlan.disableZoom();
this.isDragged = false;
var node_id = this.node.id;
this.data('origTransform', this.transform().local );
}
var dragNode = function(dx,dy) {
this.isDragged = true;
realZoom = panZoomPlan.getSizes().realZoom;
var rdx = dx/realZoom;
var rdy = dy/realZoom;
this.attr({
transform: this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [rdx, rdy]
});
event.preventDefault();
}
var dragStop = function() {
panZoomPlan.enablePan();
panZoomPlan.enableZoom();
if (!this.isDragged) {
return;
}
//update scene elements data
var node_id = this.node.id;
Nodes_dict[node_id].x += Nodes_dict[node_id].rdx;
Nodes_dict[node_id].y += Nodes_dict[node_id].rdy;
}
I hope this helps later users who are seeing this question.

Creating a click event in Javascript Canvas

I'm having trouble creating a click event for my Javascript canvas game. So far I have been following a tutorial, however the way you interact with the game is through mouse hover. I would like to change it so that instead of hovering over objects in the canvas to interact, I instead use a mouse click.
The following is the code I use to detect the mouse hover.
getDistanceBetweenEntity = function (entity1,entity2) //return distance
{
var vx = entity1.x - entity2.x;
var vy = entity1.y - entity2.y;
return Math.sqrt(vx*vx+vy*vy);
}
testCollisionEntity = function (entity1,entity2) //return if colliding
{
var distance = getDistanceBetweenEntity(entity1,entity2);
return distance < 50;
}
I then use this in a loop to interact with it.
var isColliding = testCollisionEntity(player,nounList[key]);
if(isColliding)
{
delete nounList[key];
player.score = player.score + 10;
}
Below is a complete copy of my game at its current state.
<canvas id="ctx" width="500" height="500" style="border:1px solid #000000;"></canvas>
<script>
var ctx = document.getElementById("ctx").getContext("2d");
ctx.font = '30px Arial';
//Setting the height of my canvas
var HEIGHT = 500;
var WIDTH = 500;
//Player class
var player =
{
x:50,
spdX:30,
y:40,
spdY:5,
name:'P',
score:0,
};
//Creating arrays
var nounList ={};
var adjectivesList ={};
var verbsList ={};
getDistanceBetweenEntity = function (entity1,entity2) //return distance
{
var vx = entity1.x - entity2.x;
var vy = entity1.y - entity2.y;
return Math.sqrt(vx*vx+vy*vy);
}
testCollisionEntity = function (entity1,entity2) //return if colliding
{
var distance = getDistanceBetweenEntity(entity1,entity2);
return distance < 50;
}
Nouns = function (id,x,y,name)
{
var noun =
{
x:x,
y:y,
name:name,
id:id,
};
nounList[id] = noun;
}
Adjectives = function (id,x,y,name)
{
var adjective =
{
x:x,
y:y,
name:name,
id:id,
};
adjectivesList[id] = adjective;
}
Verbs = function (id,x,y,name)
{
var verb =
{
x:x,
y:y,
name:name,
id:id,
};
verbsList[id] = verb;
}
document.onmousemove = function(mouse)
{
var mouseX = mouse.clientX;
var mouseY = mouse.clientY;
player.x = mouseX;
player.y = mouseY;
}
updateEntity = function (something)
{
updateEntityPosition(something);
drawEntity(something);
}
updateEntityPosition = function(something)
{
}
drawEntity = function(something)
{
ctx.fillText(something.name,something.x,something.y);
}
update = function ()
{
ctx.clearRect(0,0,WIDTH,HEIGHT);
drawEntity(player);
ctx.fillText("Score: " + player.score,0,30);
for(var key in nounList)
{
updateEntity(nounList[key]);
var isColliding = testCollisionEntity(player,nounList[key]);
if(isColliding)
{
delete nounList[key];
player.score = player.score + 10;
}
}
for(var key in adjectivesList)
{
updateEntity(adjectivesList[key])
var isColliding = testCollisionEntity(player,adjectivesList[key]);
if(isColliding)
{
delete adjectivesList[key];
player.score = player.score - 1;
}
}
for(var key in verbsList)
{
updateEntity(verbsList[key])
var isColliding = testCollisionEntity(player,verbsList[key]);
if(isColliding)
{
delete verbsList[key];
player.score = player.score - 1;
}
}
if(player.score >= 46)
{
ctx.clearRect(0,0,WIDTH,HEIGHT);
ctx.fillText("Congratulations! You win!",50,250);
ctx.fillText("Refresh the page to play again.",50,300);
}
}
Nouns('N1',150,350,'Tea');
Nouns('N2',400,450,'Park');
Nouns('N3',250,150,'Knee');
Nouns('N4',50,450,'Wall');
Nouns('N5',410,50,'Hand');
Adjectives('A1',50,100,'Broken');
Adjectives('A2',410,300,'Noisy');
Verbs('V1',50,250,'Smell');
Verbs('V2',410,200,'Walk');
setInterval(update,40);
To summarize all I want to do is change it so that instead of mousing over words to delete them you have to click.
(Apologies for not using correct terminology in places, my programming knowledge is quite limited.)

You can have your canvas listen for mouse clicks on itself like this:
// get a reference to the canvas element
var canvas=document.getElementById('ctx');
// tell canvas to listen for clicks and call "handleMouseClick"
canvas.onclick=handleMouseClick;
In the click handler, you'll need to know the position of your canvas relative to the viewport. That's because the browser always reports mouse coordinates relative to the viewport. You can get the canvas position relative to the viewport like this:
// get the bounding box of the canvas
var BB=canvas.getBoundingClientRect();
// get the left X position of the canvas relative to the viewport
var BBoffsetX=BB.left;
// get the top Y position of the canvas relative to the viewport
var BBoffsetY=BB.top;
So your mouseClickHandler might look like this:
// this function will be called when the user clicks
// the mouse in the canvas
function handleMouseClick(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// get the canvas postion relative to the viewport
var BB=canvas.getBoundingClientRect();
var BBoffsetX=BB.left;
var BBoffsetY=BB.top;
// calculate the mouse position
var mouseX=e.clientX-BBoffsetX;
var mouseY=e.clientY-BBoffsetY;
// report the mouse position using the h4
$position.innerHTML='Click at '+parseInt(mouseX)+' / '+parseInt(mouseY);
}
If your game doesn't let the window scroll or resize then the canvas postion won't change relative to the viewport. Then, for better performance, you can move the 3 lines relating to getting the canvas position relative to the viewport to the top of your app.
// If the browser window won't be scrolled or resized then
// get the canvas postion relative to the viewport
// once at the top of your app
var BB=canvas.getBoundingClientRect();
var BBoffsetX=BB.left;
var BBoffsetY=BB.top;
function handleMouseClick(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// calculate the mouse position
var mouseX=e.clientX-BBoffsetX;
var mouseY=e.clientY-BBoffsetY;
// report the mouse position using the h4
$position.innerHTML='Click at '+parseInt(mouseX)+' / '+parseInt(mouseY);
}

making a gravity effect inside html5 canvas

I am trying to change the position of a circle inside a canvas using random x and y when hitting the space bar but i am stuck to figure out how I should implement a gravity effect so when the circle change it's position it come back down to the ground in a smoothy way
my jsfiddle :http://jsfiddle.net/seekpunk/efcnM/5/
how can i modify my update function to succeed my gravity effect
function update() {
$(window).keydown(function (e) {
var spacebarHit = e.which == 32 || e.keyCode == 32 ? true : false;
if (spacebarHit) {
Bluecircle.y -=1;// RandomPos;
Draw();
}
});
}

Why not use the real-world equations of motion?
if (spacebarHit) {
var oldPos = Bluecircle.y;
var u = 50;
var g = 9.81;
var t = 0;
var handle = setInterval(function () {
t++;
Bluecircle.y = oldPos-(((u)*t-(g/2)*t*t));
console.log(Bluecircle.y);
if (Bluecircle.y>oldPos) {
Bluecircle.y = oldPos;
clearInterval(handle);
}
}, 100);
Draw();
}
DEMO

Use Newtonian integration:
function mainLoop(dt) {
circle.acc.x = 0
circle.acc.y = 9.81 // positive is down
circle.vel.x += circle.acc.x * t
circle.vel.y += circle.acc.y * t
circle.pos.x += circle.vel.x * t
circle.pos.y += circle.vel.y * t
// check if the bottom of the screen has been hit, and
// clamp circle.poa to he within the world
// do bounces by flipping the sign of components of circle.vel
}
function jump() {
circle.vy = -20; // or something
}

Particles with CSS and JavaScript

I'm trying to create something like a very simple particle system. No physics required at this point, just divs that are animated to look like bubbles, or bees, or whatever. The code below creates the divs and through CSS I can make them change position, floating upwards. But I can't seem to workout how to destroy particles. Each particle does it's motion and then returns back to it's original point. I would prefer if it was removed completely.
Thank you.
/* ==================== PARTICLES CONTROLLER ==================== */
/**
* Particle controller interates through all elements with
* CSS class name PARTICLE_CSS and when found a ParticleController is instantiated
* for each of the elements.
*/
function ParticleBaseController(){
var ParticleContainer = document.querySelectorAll(PARTICLE_CSS),
ParticleContainerLength = ParticleContainer.length;
for (var i = ParticleContainerLength - 1; i >= 0; i--){
new ParticleController(ParticleContainer[i]);
};
};
function ParticleController(element) {
var particleElement, fragment = document.createDocumentFragment();
var numberOfParticles = 1;
for (var i = 0; i < numberOfParticles; i ++) {
particleElement = document.createElement("div");
particleElement.addClassName(PARTICLE_ELEMENT_CSS_CLASS);
var Ypos = Math.floor((Math.random()*200)+1);
var Xpos = Math.floor((Math.random()*200)+1);
particleElement.style.top = Ypos + "px";
particleElement.style.left = Xpos + "px";
fragment.appendChild(particleElement);
}
element.appendChild(fragment);
setTimeout(ParticleBaseController, 3000);
};

This worked for me. I am guessing that the way it works is that particles are only appended to the container as long as there are fewer than 15. Although I do not know how they are actually destroyed. But on screen I can only ever see 15 particles at a time, or however many I set then number to.
/* ==================== PARTICLES CONTROLLER ==================== */
const NumberOfParticles = 15;
function smoking()
{
var container = document.getElementById('particleContainer');
for (var i = 0; i < NumberOfParticles; i++)
{
container.appendChild(createParticle());
}
}
function randomFloat(low, high)
{
return low + Math.random() * (high - low);
}
function createParticle()
{
var particleDiv = document.createElement('div');
particleDiv.style.top = "-300px";
particleDiv.style.left = "200px"
particleDiv.style.webkitAnimationName = 'smoke-rise, smoke-fade';
var SmokeDuration = randomFloat(5, 10)+"s";
var FadeDuration = randomFloat(4, 11)+"s";
var SmokeDelay = randomFloat(0, 5)+"s";
var FadeDelay = randomFloat(2, 9)+"s";
particleDiv.style.webkitAnimationDuration = SmokeDuration + ', ' + FadeDuration;
particleDiv.style.webkitAnimationDelay = SmokeDelay + ', ' + FadeDelay;
return particleDiv;
}
window.addEventListener("DOMContentLoaded", smoking, false);