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How can I get and set style properties of an object that come from a class?

I have a simple animation function that simulates a button being pushed, by varying the width:
function bPress(b) {
var w = (parseFloat(b.style.width)*0.96);
if (b.style.width.substr(-1)=="%") {
var s ="%";
}
else {
var s = "em";
}
b.style.width = w +s;
b.onmouseup = function () {
w = (parseFloat(b.style.width)/0.96);
b.style.width = w+s;
// etc.
}
This was working well until I started cleaning up my code and changed inline CSS style declarations to classes. I previously had, for example:
<div style= 'height: 1.5em; width: 100%; margin: 0 auto; margin-top: 0.2em; font: inherit; font-weight:bold' onclick='checkSave("continue")' onmousedown='bPress(this)'>Continue</div>
I moved the CSS parts to a new class:
.response_button {
height: 1.5em;
width: 100%;
margin: 0 auto;
margin-top: 0.2em;
font: inherit;
font-weight:bold
}
... avoiding repetition and of course simplifying the div tags.
But the animations stopped working. After some experimenting, I eventually came up with a temporary solution by moving the width back into an inline style declaration. But this seems wrong.
So 2 questions:
Why does this.style.width not work if the width is declared inside a class?
Is there a way to get and set a div's properties if they are declared inside a class?
Edit: For completeness, using nick zoum's answer, here is the modified bPress function:
function bPress(b) {
var w_px = window.getComputedStyle(b).width;
var w_int = (parseInt(w_px));
b.style.width = Math.round(w_int * 0.96) + "px";
b.onmouseup = function () {
b.style.width = w_px;
}
}

You can use getComputedStyle to get all of the calculated style properties of an element.
var dom = document.querySelector("#foo");
console.log(getComputedStyle(dom).backgroundColor);
#foo {
background-color: red;
width: 10px;
height: 10px;
}
<div id="foo"></div>

Fill parent div with the image being hovered over

I am still fairly new to JS, and I am trying to replace the HTML of a div with a picture that is being moused over, and when the mouse leaves I want it to return to it's normal state. I thought that I did everything right but my code doesn't seem to be working. I've looked through stack overflow and I see a lot of jQuery solutions to my 'problem,' but I would like an answer in pure JavaScript (I'm trying to "maser" this first), along with an explanation so I can understand why the answer IS the answer. Thanks.
I'll try to explain myself (my code). I grabbed reference to the image holder, and I grabbed reference to the the images. I thought I made a function that looped through the array of images and added an event listener to whichever image ( image[i] ) was being moused over. Then, I added an event listener that is supposed to return the image holder to it's default state by inserting the original HTML. I just don't understand how to fix this.
var holder = document.getElementById('holder');
var images = document.getElementsByTagName('img');
var popImage = function () {
for (i = 0; i < images.length; i++) {
images[i].addEventListener('mouseover', = function () {
holder.innerHTML = images[i];
});
images[i].addEventListener('mouseout', function () {
holder.innerHTML =
'<div class='col-md-3 img-fluid' id='img1'><img src='photo1.jpg'></div>
<div class='col-md-3 img-fluid' id='img2'><img src='photo2.jpg'></div>
<div class='col-md-3 img-fluid' id='img3'><img src='photo3.2.jpg'></div>
<div class='col-md-3 img-fluid' id='img4'><img src='photo4.jpg'></div>'
});
};
};
popImage();

You said you are new to JS and just learning which is great but an important part of learning JS is learning when not to use it. As #Yoda said if this was for production you really should use CSS instead of JS.
Here is one way you could accomplish this with pure CSS
<style>
.img {
width: 100px;
height: 100px;
background: #bada55;
border: 2px solid #333;
float: left;
}
.holder:hover > .img {
opacity: 0;
}
.holder:hover > .img:hover {
opacity: 1;
}
</style>
<div class="holder">
<!-- Using div.img for simplicity, these whould be your <img/> tags -->
<div class="img">1</div>
<div class="img">2</div>
<div class="img">3</div>
<div class="img">4</div>
</div>
For the purpose of learning, here's how you'd do it in JS:
var holder = document.getElementById('holder');
var images = document.querySelectorAll('.img');
var filter = false;
function popImage () {
// Use for (var i = 0 . . .
// Instead of for (i = 0 . . .
// Because without var, i will be stored in the global scope
for (var i = 0; i < images.length; i++) {
(function (_i) {
images[_i].addEventListener('mouseover', function () {
holder.innerHTML = '';
// We can't set innerHTML to images[_i]
// because it's a DomNode not a string
holder.appendChild(images[_i]);
});
})(i);
}
holder.addEventListener('mouseout', function (e) {
if (e.target !== holder)
return;
holder.innerHTML = '';
// Again, use var j = 0 . . .
for (var j = 0; j < images.length; j++) {
holder.appendChild(images[j]);
}
});
}
popImage();
.img {
width: 100px;
height: 100px;
background: #bada55;
border: 2px solid #333;
display: inline-block;
}
#holder {
position: relative;
width: 100%;// So doesn't collape and trigger mouseout
height: 100px;
background: red;
padding: 20px 0;
}
<div id="holder">
<!-- Again, these would be your image tags -->
<div class="img">1</div>
<div class="img">2</div>
<div class="img">3</div>
<div class="img">4</div>
</div>

I had 10 mins before leaving work so I had a crack at this to see how I would do it and give you some ideas.
Here is my implementation (https://jsfiddle.net/hg7s1pyh/)
I guess the main thing here is that I've broken it down into lots of smaller parts, this makes solving problems far easier, each method is concerned with doing one thing only.
You will also note the use of classes to show and hide content rather than removing it entirely, this takes lots of the arduous work out of this feature.
function attachEvents() {
var images = getImages();
images.forEach(function(image) {
attachMouseOverEvent(image);
attachMouseLeaveEvent(image);
});
}
function attachMouseOverEvent(element) {
element.addEventListener('mouseover', function(e) {
var clonedImage = e.target.cloneNode();
addImageToPreview(clonedImage);
});
}
function attachMouseLeaveEvent(element) {
element.addEventListener('mouseleave', function(e) {
removeImageFromPreview();
});
}
function getImages() {
return document.querySelectorAll('.js-image');
}
function getImagePreviewElement() {
return document.querySelector('.js-image-box');
}
function addImageToPreview(imageElement) {
var previewElement = getImagePreviewElement();
previewElement.classList.add('previewing');
previewElement.appendChild(imageElement);
}
function removeImageFromPreview() {
var previewElement = getImagePreviewElement();
previewElement.classList.remove('previewing');
var image = previewElement.querySelector('.js-image');
image.remove();
}
attachEvents();
.image-box {
position: relative;
min-height: 400px;
width: 400px;
border: 1px solid #000;
text-align: center;
}
.image-box .placeholder {
position: absolute;
top: 50%;
text-align: center;
transform: translateY(-50%);
width: 100%;
}
.image-box.previewing .placeholder {
display: none;
}
.image-box .image {
position: absolute;
top: 50%;
text-align: center;
transform: translate(-50%, -50%);
height: 100%;
width: 100%;
}
.images {
margin-top: 10px;
}
<div class="js-image-box image-box">
<div class="placeholder">
Placeholder
</div>
</div>
<div class="images">
<div class="col-md-3 img-fluid"><img class="js-image image" src="http://placehold.it/350x150"></div>
<div class="col-md-3 img-fluid"><img class="js-image image" src="http://placehold.it/150x150"></div>
<div class="col-md-3 img-fluid"><img class="js-image image" src="http://placehold.it/400x400"></div>
<div class="col-md-3 img-fluid"><img class="js-image image" src="http://placehold.it/350x150"></div>
</div>

getElementByID returns null (jsfiddle inside)

I'm trying to create custom buttons for a media player. The tricky part is that I want the play button to become a "loading" button that will later become a pause button but anyways.
I'm using 4 divs - stop / play / loading / pause, the last two being hidden (display:none;). I want to display the loading div instead of the play div when you click on the latter (in addition to activating the player). Yet when I call lyricsPlay("B"),document.getElementById("lyrics" + el + "1") seems to be returning null.
The stop button closes the container div (a popup which will contain the player), and stops the player. This part works fine.
Being pretty much a newbie when it comes to javascript, I'm sure this is a stupid mistake on my part but I'm at a complete loss in finding where it is. I've read many posts about getElementById() returning null but none of the solutions seems to apply to my case.
Below is my HTML code, but you can fiddle with it here:
function lyricsToggle(div_id) {
var el = document.getElementById(div_id);
if (el.style.display == 'none') {
el.style.display = 'block';
} else {
el.style.display = 'none';
}
}
function lyricsStop(videoID, divID) {
lyricsToggle(divID);
//jQuery('#lyrics' + videoID).tubeplayer('stop');
}
function lyricsPlay(el) {
var play = document.getElementById("lyrics" + el + "1"); //returns null??
var load = document.getElementById("lyrics" + el + "2"); //returns null??
lyricsToggle(play);
lyricsToggle(load);
//jQuery(video).tubeplayer("play");
}
#container {
margin-top: 60px;
margin-right: 100px;
}
.lyricsPlay {
width: 30px;
height: 30px;
float: right;
background-color: green;
}
.lyricsStop {
width: 30px;
height: 30px;
float: right;
background-color: red;
}
.lyricsLoad {
width: 30px;
height: 30px;
float: right;
display: none;
background-color: blue;
}
.lyricsPause {
width: 30px;
height: 30px;
float: right;
display: none;
background-color: yellow;
}
<body>
<div id="container">
<div id="lyricsB0" class="lyricsStop" onClick="lyricsStop('B', 'container')">
stop
</div>
<div id="lyricsB1" class="lyricsPlay" onClick="lyricsPlay('B')">
play
</div>
<div id="lyricsB2" class="lyricsLoad" onClick="lyricsLoad('B')">
loading
</div>
<div id="lyricsB3" class="lyricsPause" onClick="lyricsPause('B')">
pause
</div>
</div>
</body>

You are passing a element as div_id already to lyricsToggle() with:
var play = document.getElementById("lyrics" + el + "1");// as div_id
lyricsToggle(play);
so no need to do this inside lyricsToggle(div_id):
var el = document.getElementById(div_id);
Try this:
function lyricsToggle(div_id) {
var el = div_id; // and not: var el = document.getElementById(div_id);
if ( el.style.display == 'none' ) { el.style.display = 'block';}
else {el.style.display = 'none';}
}
Fiddle

javascript chatbox / messenger script

I'm trying to write a facebook like chatbox, but i've encountered a small problem.
I'm using the following code (it's only test code, so it's not really clean):
css code:
#messenger {
position: fixed;
bottom: 0px;
right: 10px;
width: 200px;
height: 300px;
z-index: 4;
background-color: #ECECEC;
border: 1px solid #000;
}
#messenger.p {
text-align: right;
}
#contacts {
margin: 5px 5px 5px 5px;
}
#chatspace {
position: fixed;
bottom: 0px;
right: 240px;
height: 20px;
left: 20px;
background-color: #ECECEC;
border: 1px solid #000;
z-index: 4;
}
.chatbox {
position: absolute;
bottom: 0px;
width: 200px;
height: 200px;
z-index: 4;
background-color: #ECECEC;
border: 1px solid #000;
}
html/javascript code:
<script type="text/javascript">
var i = 0;
function oc_chatbox() {
if (i == 0) {
document.getElementById('contacts').style.visibility = 'hidden';
document.getElementById('messenger').style.height = '20px';
i = 1;
}
else {
document.getElementById('contacts').style.visibility = 'visible';
document.getElementById('messenger').style.height = '300px';
i = 0;
}
}
function new_chat(userid) {
var new_right;
new_right = document.getElementById('messenger').style.right;
//alert('old value: '+ new_right);
new_right += 20;
//alert('New value of right: '+ new_right);
document.getElementById('chatspace').innerHTML = '<div id="'+userid+'" class="chatbox" style="right: '+new_right+'px;"></div>';
//document.write('<div id="'+userid+'" class="chatbox" style="right: '+new_right+'px;"></div>');
}
</script>
<div id="chatspace"></div>
<div id="messenger">
<p>Collapse</p>
<div id="contacts">
<ul>
<li>contact A</li>
</ul>
</div>
</div>
the problem is, that when I try to add new chats to the chatbar, i can't seem the place them next to each other.
anyone who can help ?
EDIT:
so i changed to javascript code to:
var last = null;
function new_chat(userid) {
if(userid==null)
userid = "user666";
var new_right;
var margin = 10;
var messenger = window.last==null?document.getElementById('messenger'):window.last; //Take the messenger or the last added chat
new_right = document.body.clientWidth-messenger.offsetLeft; //Compute the window size
console.log(new_right); //Log the number
new_right += margin; //keep spaces between divs
var newChat = document.createElement("div"); //DOM create DIV
newChat.id = userid;
newChat.className = "chatbox shadow";
newChat.style.right = new_right+"px";
newChat.innerHTML = '<p>'+userid+'</p><p><textarea></textarea></p>';
window.last = newChat; //Remember whichever is last
document.body.appendChild(newChat);
}
and now it works, thanks !

You cannot get an element right offset using its style, unlest the style is set and valid. Instead you must get element.offsetLeft and size of window area and do this:
new_right = windowSize()[0]-messenger.offsetLeft;
Where window size is this function.
Here is my, working, version of your function:
var last = null;
function new_chat(userid) {
if(userid==null)
userid = "user666";
var new_right;
var margin = 20;
var messenger = window.last==null?document.getElementById('messenger'):window.last; //Take the messenger or the last added chat
new_right = windowSize()[0]-messenger.offsetLeft; //Compute the window size
console.log(new_right); //Log the number
new_right += margin; //keep spaces between divs
var newChat = document.createElement("div"); //DOM create DIV
newChat.id = userid;
newChat.className = "chatbox";
newChat.style.right = new_right+"px";
window.last = newChat; //Remember whichever is last
document.body.appendChild(newChat);
}
You may get errors if console is not defined in your brouwser. But in such case you should take a better browser. Normally, the if(console!=null) is put in code.
And here is the link.

You should try adding a float style.
.chatbox {
float: right;
}
Add that to your chatbox styles. You may need to mess around a bit to make sure the float doesn't mess with your other elements. You may need a better container for them.
If you want to get really fun, you can add .draggable() from jQuery, and you can have them snap to your chat bar. You can then change the order of your chats.

Make element move by using Javascript

I am trying to make a webpage where when you click a link, the link moves diagonally every 100 milliseconds.
So I have my Javascript, but right now when I click the link nothing happens
Also, does anyone know of a Javascript IDE I can use to make sure I have no errors in my code?
PS: Does anyone know why my elements dont stretch to fit the whole 200px by 200px of the div element? The links are only small when they should be the same width as their parent div element.
Edited with new advice, although still wont move.
<script LANGUAGE="JavaScript" type = "text/javascript">
<!--
var block = null;
var clockStep = null;
var index = 0;
var maxIndex = 6;
var x = 0;
var y = 0;
var timerInterval = 100; // milliseconds
var xPos = null;
var yPos = null;
function moveBlock()
{
if ( index < 0 || index >= maxIndex || block == null || clockStep == null )
{
clearInterval( clockStep );
return;
}
block.style.left = xPos[index] + "px";
block.style.top = yPos[index] + "px";
index++;
}
function onBlockClick( blockID )
{
if ( clockStep != null )
{
return;
}
block = document.getElementById( blockID );
index = 0;
x = parseInt( block.style.left, 10 );
y = parseInt( block.style.top, 10 );
xPos = new Array( x+10, x+20, x+30, x+40, x+50, x+60 );
yPos = new Array( y-10, y-20, y-30, y-40, y-50, y-60 );
clockStep = self.SetInterval( moveBlock(), timerInterval );
}
-->
</script>
<style type="text/css" media="all">
<!--
#import url("styles.css");
#blockMenu { z-index: 0; width: 650px; height: 600px; background-color: blue; padding: 0; }
#block1 { z-index: 30; position: relative; top: 10px; left: 10px; background-color: red; width: 200px; height: 200px;
margin: 0; padding: 0; /* background-image: url("images/block1.png"); */ }
#block2 { z-index: 30; position: relative; top: 50px; left: 220px; background-color: red; width: 200px; height: 200px;
margin: 0; padding: 0; /* background-image: url("images/block1.png"); */ }
#block3 { z-index: 30; position: relative; top: 50px; left: 440px; background-color: red; width: 200px; height: 200px;
margin: 0; padding: 0; /* background-image: url("images/block1.png"); */ }
#block4 { z-index: 30; position: relative; top: 0px; left: 600px; background-color: red; width: 200px; height: 200px;
margin: 0; padding: 0; /* background-image: url("images/block1.png"); */ }
#block1 a { display: block; width: 100%; height: 100%; }
#block2 a { display: block; width: 100%; height: 100%; }
#block3 a { display: block; width: 100%; height: 100%; }
#block4 a { display: block; width: 100%; height: 100%; }
#block1 a:hover { background-color: green; }
#block2 a:hover { background-color: green; }
#block3 a:hover { background-color: green; }
#block4 a:hover { background-color: green; }
#block1 a:active { background-color: yellow; }
#block2 a:active { background-color: yellow; }
#block3 a:active { background-color: yellow; }
#block4 a:active { background-color: yellow; }
-->
</style>

Errors needed to fix
To fill the width of the div elements, the a elements need to be display: block; not their default display: inline;.
Knowing runtime errors is more important in my opinion, and IDEs don't catch DOM errors or anything more complex than syntax; use the error logging in your browser (Firefox's is called Error Console). That'll also catch in-development errors like syntax errors.
This is the most important point to stress: block.style.left and block.style.top are not just numbers with implicit pixel values in them. Setting it to a number without a unit suffix will do absolutely nothing. You need to add % or px or whatever unit when setting left and top.
When getting the current value, as in var x = ... and var y = ..., you need to Number() manually to get the numeric portion of the string.
Also, I believe you meant || block == null, not =, which would set block to null.
Tips
You can use moveBlock instead of "moveBlock();" as an argument to setTimeout. This avoids parsing the string into code, and avoids scope problems (though not in this example as moveBlock is global).
I know that you have an array of values, where both x and y move 10 each time. I assume you want to move at a 45 degree angle. If so, this won't work as you expect even after fixing all the errors as x is percentage and y is in pixels.

You should declare your x and y above like your other variables. It may work but its confusing.
in your setTimeout, use moveBlock, not "moveBlock()" - it will save the step of evaluating your string into code.
block.style.left will return a string that includes "px" - it won't be a number. You can do:
x = Number(x);
//or
x = parseInt(x, 10);
When you set the position, remember to add the "px":
block.style.left = xPos[index] + "px";
EDIT:
Ok, the key problem is 'style.left' is not reading because it was set with CSS and not the style object. I use my library to get the style which runs through a few scenarios and catches that automatically. So change these lines to (this may not be exactly correct but will get things moving):
x = parseInt( node.style.left, 10 ) || 0;
y = parseInt( node.style.top, 10 ) || 0;
Also, this is wrong (you never declared 'self', and you don't need it here anyway; JS is case sensitive, SetInterval is not capped; pass the function, not the function result):
clockStep = self.SetInterval( moveBlock(), timerInterval ); // <-- result of moveBlock
// change to:
clockStep = setInterval( moveBlock, timerInterval ); // <-- the function moveBlock
During dev, you should remove the if() statements that could have been blocking the code and just put a simple count--; in there. It's really hard to debug code when you have literally 20 things wrong. Write a line, test. Write a line, test.
You have HTML comments in the script and style blocks. This is from 1998. While they don't hurt anything intact, in the past I've accidentally edited my code and removed one of them, and this will throw everything out of whack - your IDE, the browser - because they won't know what's wrong and you won't get a good error message.
LANGUAGE="JavaScript" is no longer used and is a waste of bytes.
To help speed development add this line:
window.onloadfunction(){
onBlockClick('block1')
}
That will execute your code right away for testing and you don't have to click every time.
Finally, I highly recommend you use Firefox and Firebug. Developing without it is like trying to build a ship in a bottle with boxing gloves. Using console.log(block.style.left) would have shown you it was not set. The error messages would have told you SetInterval and moveBlock() was incorrect. You do need to remember to remove the console.logs before production though. or... (shameless plug)... use my JavaScript Console Fix library which will do that for you: http://clubajax.org/javascript-console-fix-v2-now-with-ios/