Develop Reference

How would I make specific boxes changes color upon clicking on them?

I'd like to change color of more than one box to purple upon clicking on it. With my current code below, only one box gets colored purple when clicking on it.
I've tried so many different ways to make it work in terms of upon you clicking on any number of boxes, the box should turn purple, but all my attempts have failed.
What am I doing wrong?
function createBoxesDynamically() {
var tileLength = Math.floor(Math.random() * 11);
console.log("tileLength " + tileLength);
var box = new Array(tileLength);
console.log("box" + box);
for (var i = 0; i < box.length; i++) {
box[i] = "box";
}
for (var j = 0; j < box.length; j++) {
var div = document.createElement("div");
div.id = "box";
document.body.appendChild(div);
}
var boxes = document.querySelector("[id^=box]");
boxes.addEventListener("click", function () {
boxes.style.backgroundColor = "purple";
});
}
createBoxesDynamically();
#box {
border: 1px solid;
width: 50px;
height: 50px;
background-color: green;
}

You can't have multiple elements with identical id values, that's why no matter which box you click, the first one is always affected, your .querySelector() call stops looking after finding the first match.
Instead, move the code that sets up the event handler inside the loop where the box is being created and just use this in the click callback to have the callback act upon the box that was clicked. No id necessary. And, because you won't be using ids, you don't need your array or the first loop.
In general, stay away from coding solutions that rely on ids. Yes, they seem precise and easy to use at first, but what you'll find (and you already are) is that they create very brittle solutions that don't scale very well. There are many other ways of referencing and styling elements besides an id.
You should also try to avoid inline styling of elements (setting up styles directly on the style property) as this usually leads to duplication of code and therefore makes the code more difficult to read and maintain. Use CSS classes for as much as you can.
function createBoxesDynamically() {
var tileLength = Math.floor(Math.random() * 11);
console.log("tileLength " + tileLength);
for (var j = 0; j < tileLength; j++) {
var div = document.createElement("div");
div.classList.add("box"); // Add the CSS class to the element
div.addEventListener("click", function () {
this.classList.add("clickColor");;
});
document.body.appendChild(div);
}
}
createBoxesDynamically();
/* Use Classes instead of IDs */
.box {
border: 1px solid;
width: 50px;
height: 50px;
background-color: green;
}
.clickColor { background-color: #800080; }

How get all computed css properties of element and its children in Javascript

I'm trying to set up a service in python using pdfKit to create a pdf file from html files.
So basically I will send my element as string and expect the server to return a pdf version of it, but to be an accurate representation I also need to send a css file of the element.
How can I do this? Generate JSON / object with only the relevant style properties and selectors of an element and all its children. Respecting hierarchy and no duplicates. There are similar questions but they are outdated and tend to not consider children elements.
I was thinking maybe there is a way to create a new DOM from this element and then get the root css?

Here is something I came up with, basically pass the element you want to extract the styles of and ones of its children, and it will return you the stylesheet as a string. Open your console before running the snippet and you will see the output from the console.log.
Because I wanted to support the extraction of every element even those without a selector, I had to replace each element id by a unique uuid specifically generated for them in order to facilitate the styling of your output. The problem with this approach is in case you are using ids for styling or for user interaction, you are going to loose such functionality on concerned elements after calling extractCSS.
However, it is pretty trivial to use the oldId I'm passing to change back once your pdfKit process finished the generation. Simply call swapBackIds passing the elements returned by the function. You can see the difference of behavior if you uncomment the call in my snippet: the #root pink background would disappear because the styling targets an element id.
All in all, you need to:
Call extractCSS with the element you want to extract
Generate your pdf using res.stylesheet
Call swapBackIds with res.elements
// Generate an unique id for your element
// From https://stackoverflow.com/a/2117523/2054072
function uuidv4 () {
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
return v.toString(16);
});
}
// Flatten an array
// https://stackoverflow.com/a/15030117/2054072
function flatten(arr) {
return arr.reduce(function (flat, toFlatten) {
return flat.concat(Array.isArray(toFlatten) ? flatten(toFlatten) : toFlatten);
}, []);
}
function recursiveExtract (element) {
var id = uuidv4()
var oldId = element.id
var computed = window.getComputedStyle(element)
var style = computed.cssText
// Now that we get the style, we can swap the id
element.setAttribute('id', id)
// The children are not a real array but a NodeList, we need to convert them
// so we can map over them easily
var children = Array.prototype.slice.call(element.children)
return [{ id: id, style: style, oldId: oldId }].concat(children.map(recursiveExtract))
}
function extractCSS (element) {
if (!element) { return { elements: [], stylesheet: '' } }
var raw = recursiveExtract(element)
var flat = flatten(raw)
return {
elements: flat,
stylesheet: flat.reduce(function (acc, cur) {
var style = '#' + cur.id + ' {\n' + cur.style + '\n}\n\n'
return acc + style
}, '')
}
}
var pdfElement = document.querySelector('#root')
var res = extractCSS(pdfElement)
console.log(res.stylesheet)
function swapBackIds (elements) {
elements.forEach(function (e) {
var element = document.getElementById(e.id)
element.setAttribute('id', e.oldId)
})
}
swapBackIds(res.elements)
#root {
background-color: pink;
}
.style-from-class {
background-color: red;
width: 200px;
height: 200px;
}
.style-from-id {
background-color: green;
width: 100px;
height: 100px;
}
<div id="root">
<span>normal</span>
<span style="background: blue">inline</span>
<div class="style-from-class">
style-class
</div>
<div class="style-from-id">
style-id
<div style="font-size: 10px">a very nested</div>
<div style="font-size: 12px; color: white">and another</div>
</div>
</div>
<div id="ignored-sibling">
</div>

let para = document.querySelector('p');
let compStyles = window.getComputedStyle(para);
para.textContent = 'My computed font-size is ' + compStyles.getPropertyValue('font-size') + ',\nand my computed background is ' + compStyles.getPropertyValue('background') + '.';
p {
width: 400px;
margin: 0 auto;
padding: 20px;
font: 2rem/2 sans-serif;
text-align: center;
background: purple;
color: white;
}
<p>Hello</p>
you can use getComputedStyle method to get computed value of style property

How to select a new added element and edit it?

I have an <a> element:
<a id='addNewElementk' onclick='//Some Js Code' class='continueButton'>Click To Add</a>
When this anchor is clicked , A new element added:
New Added Element
And the first anchor which was clicked , Is removed.
I want to select that new element.
I tried:
window.onload = function(){
var newElem = document.getElementsByClassName('continueButton')[1];
alert(newElem.innerHTML);
}
I'm using ('continueButton')[1] , As there is another input with the same class before that anchor.
But for sure I get Click To Add from the first one , As that's was found when the page is loaded.
So how can I select that new element?

You're attempting to select the element before it exists in the DOM.
You instead need to run that code within the click event handler of the first <a>, like this:
window.onload = function() {
document.querySelector('#addNewElementk').addEventListener('click', function(e) {
e.preventDefault();
var a = document.createElement('a');
a.textContent = 'New Added Element';
a.href = '#';
a.classList.add('continueButton');
a.addEventListener('click', function(e) {
console.log(a.innerHTML);
});
this.parentNode.insertBefore(a, this);
this.remove();
});
}
<a id='addNewElementk' href="#" class='continueButton'>Click To Add</a>
Note the use of addEventListener() over the outdated on* event attributes which should be avoided.

You are attempting to select on an element that doesn't exist in the DOM. Dynamically added elements can be accessed in a couple of ways, above someone has an answer that adds an event listener to the created element which is a solid solution. The other most common way would be to use event delegation (if you are familiar with jQuery that would be $(parentElement).on('action', 'elementWeWantToWatch', function)) in Vanilla js the pattern is effectively the same, find or make a container element for your dynamic html, then add a listener to that container. Inside the listener you will want to ensure the target matches whatever your dynamic selection would be and execute when you find a match.
In this Example
The event listener is initiated on page load to watch the container element. The listener watches for clicks on elements with the continueButton class and when it finds one it removes the clicked element and adds a new element (the counter is to demonstrate that new content is being displayed :D)
(function() {
let i = 1;
const makeButton = () => {
const a = document.createElement('a');
a.classList.add('continueButton');
a.href = '#';
a.textContent = `Button ${i}`
i++;
return a;
}
const init = () => {
const container = document.querySelector('.test');
container.addEventListener('click', e => {
if (e.target.classList.contains('continueButton')) {
let button = makeButton();
container.appendChild(button);
container.removeChild(e.target);
return;
}
});
};
if (document.readyState == 'loading') {
window.addEventListener('DOMContentLoaded', init);
} else {
init();
}
})()
.test {
width: 100%;
display: block;
text-align: center;
}
.continueButton {
display: block;
color: white;
background-color: green;
border-radius 2px;
padding: 15px 30px;
line-height: 2;
margin: 50px auto;
width: 200px;
text-decoration: none
}
<section class="test">
<a id='addNewElementk' class='continueButton'>Click To Add</a>
</section>

Removing JavaScript behavior

I need to remove the JavaScript behavior that I set on a div.
First, I set the CSS (it's an simple example) :
#redBloc {
width: 100px;
height: 50px;
background-color: #ad3232;
}
#redBloc:hover {
background-color: #3270ad;
}
Okay, for some reasons I need to override the behavior when the mouse is over my div.
var redBloc = document.getElementById('redBloc');
redBloc.onmouseover = function() {
this.style.backgroundColor = 'red';
};
It works like I want.
But later in my process, I need to reset the JavaScript behavior, to retrieve the behavior written in my CSS file.
How can I do this ?
Thank you
EDIT
I didn't need to override the behavior on the onmouseleave event, but later in my code, by the press of a button "disable behavior" for example.
That was solved by the solution of #T.J.Crowder.
Thank you all !

I think you mean you want to remove the specific background color so that the one from CSS can show through again (rather than "behavior").
If so, assign "" to it:
theElement.style.backgroundColor = "";
If you really do mean behavior and you don't want that mouseover handler to fire anymore, since you've used onmouseover to assign it, you can remove it by assigning null:
theElement.onmouseover = null;

Make your element null on mouseout, like:
var redBloc = document.getElementById('redBloc');
redBloc.onmouseover = function() {
this.style.backgroundColor = 'red';
};
redBloc.onmouseout = function() {
this.style.backgroundColor = '';
};
Have a look at the snippet below:
var redBloc = document.getElementById('redBloc');
redBloc.onmouseover = function() {
this.style.backgroundColor = 'red';
};
redBloc.onmouseout = function() {
this.style.backgroundColor = '';
};
#redBloc {
width: 100px;
height: 50px;
background-color: #ad3232;
}
#redBloc:hover {
background-color: #3270ad;
}
<div id="redBloc"></div>
Hope this helps!

You can remove the effect when user leaves your element using onmouseleave & null the style attribute:
var redBloc = document.getElementById('redBloc');
redBloc.onmouseover = function() {
this.style.backgroundColor = 'red';
};
redBloc.onmouseleave = function() {
this.style.backgroundColor = "";
};
<span id="redBloc">Hover me & leave me!</span>

You need to remove the style attribute by running the this code
var redBloc = document.getElementById('redBloc');
redBloc.removeAttribute('style')
You can have functionality on onmouseleave
redBloc.onmouseleave = function(){
this.removeAttribute('style');
}

You want to give redBloc the style with id #redBloc defined in Your css ... What You can do is create a css class and put all the styles in it that you want to apply on redBloc
.redBloc {
width: 100px;
height: 50px;
background-color: #ad3232;
}
then in your javascript you can add this class to redBloc on mouseover
var redBloc = document.getElementById('redBloc');
redBloc.onmouseover = function() {
this.className += " redBloc";
};
and this will add those styles defined in redBloc css class on your redBloc div. Hope this helps !

Insert node as string but keep the instance of the node

I want to insert a node, that is converted to a string, on a specific position.
the problem is that i want to keep or regain the instance of the node, but dont know how.
I hope some of you have a solution
Note: I have to insert the element as string!
HTML:
<div class="div">
Here are <span class="span"></span> some text
</div>
CSS:
.div, .span {
display: inline-block;
border: 1px solid #333333;
width: 200px;
height: 100px;
}
.span {
min-width: 10px;
max-width: 50px;
height: 50px;
}
JS:
var div = document.querySelector('.div');
var span = document.querySelector('.span');
// element to insert
var newElement = document.createElement('div');
newElement.innerHTML = 'Hallo!';
// convert to string
var converter = document.createElement('div');
converter.appendChild(newElement);
// insert element at the end of span
span.innerHTML = span.innerHTML + converter.innerHTML;
// get the instance of the node? to interact with it
newElement.style.color = '#00ff00';
Example: CODEPEN

I wrote small function for test:
function makeNode(innerHTML){
var node = document.createElement('div');
node.id = 'unique_id';
node.innerHTML = innerHTML;
document.body.innerHTML += node.outerHTML;
return document.getElementById('unique_id');
}
Create element, insert in body, and return it
var elm = makeNode('test div');
Apply some style
elm.style = 'color:red;';
Try it: https://jsfiddle.net/nv6gyLve/

You need to set styles before insert element to dom. Other way -getElementById or same functions