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Simple Collision Detection in Javascript / Jquery?

I am working on a portion of a project that I am trying to detect when certain divs hit each other. In the code that I made, that doesn't work, I basically say take the first div's left amount, compare it to the other div's left amount, if they are within a certain amount it triggers an alert. If I get that much to work I am going to implant a way to say that if the distance between the two divs is 0 then it will run a certain function. I am afraid the scope of this project is too big for me, even though I am basically at the last part, because I have spent hours researching a simple way to add collision detection, but everything I find looks like rocket science to me, that is why I tried to create my own way below. So in summary, what I want to know is why my collision detection code doesn't work, how I can make it work if possible, and if not possible what is the next best option that I should use.
//Collision
function collision(){
var tri = $('#triangle');
var enemyPos = $('.object1').css('left');
var minHit = enemyPos - 32.5;
var maxHit = enemyPos + 32.5;
var triLoc = tri.css('left');
if(triLoc > minHit && triLoc < maxHit){
alert('hit');
}
}
collision();
}
}
full code: https://jsfiddle.net/kc59vzpy/

If the code you have above is definitely where the problem is, then you need to look at the enemyPos variable. Getting the left position also adds px, so enemyPos is 100px or something like that. When you add 32.5, you get 100px32.5 and when you subtract you get NaN, neither of which you want.
Before you add or subtract, use enemyPos = parseInt($('.object1').css('left')); to turn it into an actual number.

Make an image appear and then grow in size in a html canvas

I was wondering if its possible to create an image using various lines and bez-curves that appears and then moves down the canvas and gets larger as it grows. The animation in question requires the room to fill with gas and so the the gas gets greater and greater as it moves around the canvas.
I had thought about just drawing the image and then using a for loop to move the image down until a certain y coordinate, but this doesnt help with the increasing part of the created image
Any help appreciated

There are different ways to make animations happen. What I normally do for my canvas games is that I have a gameloop that loops at a certain FPS that I decide at the start of my project. Each animation is normally controlled by time an speed.
var fps = 60;
var lastUpdateTime = +new Date(); //when did I last update the game?
function gameloop() {
var updateStartTime = +new Date();
update(updateStartTime-lastUpdateTime); //update the game for the according to the elapsed time since last update
lastUpdateTime = updateStartTime;
//Normally I also handle spawning stuff here
//I also remove old object in my gameloop
setTimeout(gameloop,1000/fps)
}
function update(elapsedTime) {
//This function update the locations of game elements such as player position, bullets, enemies, bananas etc. (or even gas clouds!)
//When I change a value, I use the time-parameter passed along with the call so that I get a smooth game even though the browser might lag.
playerX += velocity*timeElapsed; //as an example
}
Here's an example on your problem where I made a function to create a gas bubble object (yes, I do know how wrong it is to use gas bubbles =P). These objects travel downwards (physics?!) and increase in size (OK, this is starting to sound more and more crazy), just have a look:
http://jsfiddle.net/Niddro/ppa4xuw8/

Moving an image up the screen using do and while loops

I am learning JavaScript and have been developing a simple game that is essentially a balloon that you can move around on the screen. I managed to do keypresses etc with a lot of help and the balloon moved about just perfectly.
I now want to simulate gravity, by having the balloon move one pixel down the screen if the balloon image was above a value, i tried to do this with the following do while statement:
var balloon = document.getElementById("balloon");
var bottom = parseInt (balloon.style.bottom, 10);
do {
balloon.style.bottom = bottom + 50 + 'px';
}
while (bottom = bottom > 600) // Gravity
What I want this to do, is to check the code is working by making the balloon move up the page 1 pixel if the bottom value is less than 600.
I have stripped out all the code I used to make the balloon move.
If I could just see the balloon move slowly up the page I would be very happy, because then at least I know I can just switch the values round when I've added the movement back in.

The other answers address the issue of attempting an animation with an explicit loop. As they have pointed out, you should use timers.
Because it seemed like fun, I made you a simple example of how to use a timer to animate a balloon falling:
http://jsfiddle.net/dmuu9w97/
The key code is the following:
// Make balloon fall 1px every 10ms
setInterval(function() {
var bottom = getBalloonBottom();
if (bottom > 0)
balloon.style.bottom = bottom - 1 + "px";
}, 10);

For your while loop condition should be (bottom>600) . No need for '='
You are loading the variable bottom outside the loop. It will never change. If it is 610 at the start of the loop it will remain 610 because it is assigned only in line 2 of your code
While loop should probably be ....bottom = (bottom - 1) + 'px';
If you write a while loop like this, it will execute 10 times immediately and your baloon will be always stuck in 600
To solve 'stuck at 600' problem, you should use a timer:
Think about "how fast should the balloon fall". Then you can come up with some number like "5 pixels in 100 milliseconds".
Then write a function... call that function on a timer.
Check the setTimeout function here...
setTimeout method

It's not impossible to do with a do loop but I think you ought to abandon this explicit loop in favor of javascript's timer/timeline. Look into how to use window.setTimeout() where the body of your do loop becomes the body of the callback function AND a trailing call to window.setTimeout() passing the callback again with a delay of 1000/your-chosen-framerate milliseconds. Then you can also process keypress events in their own handlers for intentional movement.
If you use an explicit loop, you'll only get gravity because the loop should never end (just as gravity never stops pulling) and therefore the browser will never have a chance to call the keypress event handler.
Your timeout callback runs once, queues itself again, and terminates. That gives control back to the browser's javascript engine to process events or, if nothing else, run the callback function again after the requested delay.

requestAnimationFrame may be more appropriate than setTimeout in modern JS implementations. It usually leads to a smoother result for animations.

JavaScript Duration of animation isn't exact

First of all I want to mention two things,
One: My code isn't perfect (esspechially the eval parts) - but I wanted to try something for my self, and see if I could duplicate the jQuery Animation function, so please forgive my "bad" practices, and please don't suggest that I'll use jQuery, I wanted to experiment.
Two: This code isn't done yet, and I just wanted to figure out what makes it work badly.
So the animation runs for about 12 seconds while the duration parameter I entered was 15 seconds, What am I doing wrong?
function animate(elem, attr, duration){
if(attr.constructor === Object){//check for object literal
var i = 0;
var cssProp = [];
var cssValue = [];
for(key in attr) {
cssProp[i] = key;
cssValue[i] = attr[key];
}
var fps = (1000 / 60);
var t = setInterval(function(){
for(var j=0;j<cssProp.length;j++){
if(document.getElementById(elem).style[cssProp[j]].length == 0){
//asign basic value in css if the object dosn't have one.
document.getElementById(elem).style[cssProp[j]]= 0;
}
var c = document.getElementById(elem).style[cssProp[j]];
//console.log(str +" | "+c+"|"+cssValue[j]);
if(c > cssValue[j]){
document.getElementById(elem).style[cssProp[j]] -= 1/((duration/fps)*(c-cssValue[j]));
}else if(c < cssValue[j]){
document.getElementById(elem).style[cssProp[j]] += 1/((duration/fps)*(c-cssValue[j]));
}else if(c == cssValue[j]){
window.clearInterval(t);
}
}
},fps);
}
}
animate('hello',{opacity:0},15000);
html:
<p id="hello" style="opacity:1;">Hello World</p>
Note: I guess there is a problem with the
(duration/fps)*(c-cssValue[j])
Part or/and the interval of the setInterval (fps variable).
Thanks in advance.

I'm not gonna try and refactor that and figure it out, cause it's pretty wonky. That said... a few things.
Don't rely on the value you are animating to let you know animation progress
In general your approach is unsound. You are better off keeping track of progress yourself. Also, as a result of your approach your math seems like it's trying too hard, and should be much simpler.
Think of it like this: your animation is complete when the time has elapsed, not when the animated value seems to indicate that it's at the final position.
Don't increment, set
Floating point math is inexact, and repeated addition cumulation like this is going accumulate floating point errors as well. And it's far more readable to make some variables to keep track of progress for you, which you can use in calculations.
animatedValue += changeOnThisFrame // BAD!
animatedValue = valueOnThisFrame // GOOD!
Don't do the positive/negative conditional dance
It turns out that 10 + 10 and 10 - (-10) is really the same thing. Which means you can always add the values, but the rate of change can be negative or positive, and the value will animate in the appropriate direction.
timeouts and intervals aren't exact
Turns out setTimeout(fn, 50) actually means to schedule the fn to be call at least 50ms later. The next JS run loop to execute after those 50ms will run the function, so you can't rely on it to be perfectly accurate.
That said it's usually within a few milliseconds. But 60fps is about 16ms for frame, and that timer may actually fire in a variable amount of time from 16-22ms. So when you do calculations based on frame rate, it's not matching the actual time elapsed closely at all.
Refactor complex math
Deconstructing this line here is gonna be hard.
document.getElementById(elem).style[cssProp[j]] -= 1/((duration/fps)*(c-cssValue[j]));
Why for more complex break it up so you can easily understand what's going on here. refactoring this line alone, I might do this:
var style = document.getElementById(elem).style;
var changeThisFrame = duration/fps;
var someOddCalculatedValue = c-cssValue[j];
style[cssProp[j]] -= 1 / (changeThisFrame * someOddCalculatedValue);
Doing this makes it clearer what each expression in your math means and what it's for. And because you didn't do it here, I had a very hard time wondering why c-cssValue[j] was in there and what it represents.
Simple Example
This is less capable than what you have, but it shows the approach you should be taking. It uses the animation start time to create the perfect value, depending on how complete the animation should be, where it started, and where it's going. It doesn't use the current animated value to determine anything, and is guaranteed to run the full length of the animation.
var anim = function(elem, duration) {
// save when we started for calculating progress
var startedAt = Date.now();
// set animation bounds
var startValue = 10;
var endValue = 200;
// figure out how much change we have over the whole animation
var delta = endValue - startValue;
// Animation function, to run at 60 fps.
var t = setInterval(function(){
// How far are we into the animation, on a scale of 0 to 1.
var progress = (Date.now() - startedAt) / duration;
// If we passed 1, the animation is over so clean up.
if (progress > 1) {
alert('DONE! Elapsed: ' + (Date.now() - startedAt) + 'ms');
clearInterval(t);
}
// Set the real value.
elem.style.top = startValue + (progress * delta) + "px";
}, 1000 / 60);
};
anim(document.getElementById('foo'), 5000);
​
JSFiddle: http://jsfiddle.net/DSRst/

You cannot use setInterval for accurate total timing. Because JS is single threaded and multiple things compete for cycles on the one thread, there is no guarantee that the next interval call will be exactly on time or that N intervals will consume the exact duration of time.
Instead, pretty much all animation routines get the current time and use the system clock to measure time for the total duration. The general algorithm is to get the start time, calculate a desired finish time (starttime + duration). Then, as you've done, calculate the expected step value and number of iterations. Then, upon each step, you recalculate the remaining time left and the remaining step value. In this way, you ensure that the animation always finishes exactly (or nearly exactly) on time and that you always get exactly to the final position. If the animation gets behind the ideal trajectory, then it will self correct and move slightly more for the remaining steps. If it gets ahead for any reason (rounding errors, etc...), it will dial back the step size and likewise arrive at the final position on time.
You may also need to know that browsers don't always support very small timing amounts. Each browser has some sort of minimum time that they will allow for a timer operation. Here's an article on minimum timer levels.
Here's an article on tweening (the process of continually recalculating the step to fit the duration exactly).
I'd also suggest that you look at the code for doing animation in some libraries (jQuery, YUI or any other one you find) as they can all show you how this is done in a very general purpose way, including tweening, easing functions, etc...

Moving elements with javascript

What are the best practices for moving elements with javascript?
Do you use timeouts or intervals?
Is it bad to have timed events for 10 milliseconds, or will it be precise?
Do you move pixel by pixel, or a certain fraction of the total distance?
If you use intervals, how do you stop the interval when the element is in position?
The last two times I've seen motion in javascript have been with jQuery and Raphael.js, neither of which I can understand the source code of. Are there some good tutorials or code examples anywhere? Is there a simple explanation of the methods jQuery uses?

There is a recent function called requestAnimationFrame which runs a function as soon as possible. This is a good practice since it has been made for animation purposes.
The way it works in terms of coding is the same as setTimeout, e.g. when the function finishes you call requestAnimationFrame.
In the function, you fetch the current time to see how the object should be positioned at that time.
You can cancel a pending function it with cancelRequestAnimationFrame, passing the return value of requestAnimationFrame.
Currently this is not cross-browser and the functions are vendor-prefixed, e.g. webkitRequestAnimationFrame for Chrome.
E.g.: http://jsfiddle.net/pimvdb/G2ThU/1/.
var div = document.getElementById('div');
var animation;
function move() {
var time = Math.round((new Date()).getTime() / 10) % 200;
div.style.left = time + 'px';
animation = requestAnimationFrame(move);
}
document.getElementById("start").onclick = function() {
animation = requestAnimationFrame(move);
}
document.getElementById("stop").onclick = function() {
cancelRequestAnimationFrame(animation);
}

Here you can find a good Javascript Animation tutorial:
http://www.schillmania.com/content/projects/javascript-animation-1
But what you said is right. Jquery Animate uses setTimeout, moving the object based in calculations of duration, position and easing.

Intervals are preferable, I believe, because you only set it once in the code rather than once per frame. It only needs to read the code once and reuse it several times, rather than reading it every time it is created.
10ms is a bit short. The computer can natively support intervals of about 16ms, then more precise timers can be used for faster intervals, however these are very power-consuming. IE9 supports both, depending on the computer's power settings, but ideally you shouldn't need anything faster than 50ms (20 FPS).
I like to move a fraction of the total distance, based on the time that has passed since the animation started. This way, no matter what the speed of the computer and browser, the animation will always take the exact same amount of time. Guaranteed.
Something like:
interval = setInterval(function() {
// do stuff
if( /*animation ended*/) clearInterval(interval);
},time);
jQuery is easy for some, but personally I find nothing beats writing it yourself in plain, old JS. Much easier to understand what's going on exactly, rather than relying on some framework to get it right for you.