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JavaScript loop over clickable elements on click event, and skip the specific clicked element

<div>
<div class="clickable">1</div>
<div class="clickable">2</div>
<div class="clickable">3</div>
<div class="clickable">4</div>
</div>
Upon clicking one of the 'clickable' elements i want to add a new class to all elements with 'clickable' class except the one that has been clicked.
$('.clickable').on('click', function (e) {
$('.clickable').each(function () {
$(this).addClass('new-class')
});
})
How, inside the loop, can i skip the specific element that was clicked?

$('.clickable').on('click', function() {
$(this).removeClass('new-class').siblings().addClass('new-class');
});

This is the simplest to control and read
You do not need the each
$('.clickable').on('click', function(e) {
$('.clickable').addClass('new-class');
$(this).removeClass('new-class');
})
.new-class {
color: red
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
<div class="clickable">1</div>
<div class="clickable">2</div>
<div class="clickable">3</div>
<div class="clickable">4</div>
</div>
If they are surely all in the same container, you can use siblings.
To chain you MUST remove before adding
$('.clickable').on('click', function(e) {
$(this)
.removeClass('new-class') // still necessary for the second click of another element
.siblings().addClass('new-class');
})
.new-class {
color: red
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
<div class="clickable">1</div>
<div class="clickable">2</div>
<div class="clickable">3</div>
<div class="clickable">4</div>
</div>

There is a not method in jQuery so the simplest thing you can do in my opinion is with the help of not method like below:
$('.clickable').on('click', function (e) {
$('.clickable').not(this).addClass('new-class');
})

Javascript Function to Click Element that is Defined with Multiple Classes

I am trying to click a button but the only thing that defines it is multiple classes. The element I want to click is
<div class="U26fgb XHsn7e obPDgb M9Bg4d">This is a button </div>
How would I go about clicking it using Javascript?

As long as it is the only <div> element with that class combination, you'd use .querySelector(), which accepts any valid CSS selector as an argument so you can select elements in JavaScript the same way you would in CSS:
// Scan the document for the <div> that has the required classes
let theDiv = document.querySelector("div.U26fgb.XHsn7e.obPDgb.M9Bg4d");
// Set up a click event handling function
theDiv.addEventListener("click", function(){
console.log("you clicked me");
});
// Trigger the click event of the <div>
theDiv.click();
<div class="U26fgb XHsn7e obPDgb M9Bg4d">Click Me</div>
FYI: You should get out of the habit of putting spaces on the insides of the < and > delimiters in HTML. Use this:
<div class="U26fgb XHsn7e obPDgb M9Bg4d">Click Me</div>
Not this:
< div class="U26fgb XHsn7e obPDgb M9Bg4d" >Click Me< /div >

very simple with jQuery:
$(".U26fgb.XHsn7e.obPDgb.M9Bg4d").click(function(){
console.log("clicked!");
});

const div = document.querySelector('div .M9Bg4d');
div.addEventListener("click", ()=> {
// here put what you wanna do after clicking the div.
});

onclick attribute works well inside almost all the html tags and here is the simple solution to click on the div and get a result. All the Best!
function clickDiv(){
console.log("Div is Clicked");
}
<div class="U26fgb XHsn7e obPDgb M9Bg4d" onclick="clickDiv()">This is a button </div>

Make div clickable, only when anchor is present in div (multiple divs)

Given a basic structure how can I turn a series of divs into links without turning every div into a link? Here's an example:
<div class="boxes">
<div class="box"><p>Some text with a link</p></div>
<div class="box"><p>Some text without a link</p></div>
<div class="box"><p>Some text with a link</p></div>
<div class="box"><p>Some text without a link</p></div>
</div>
And the associated jQuery I'm using to make the divs clickable:
$(document).ready(function() {
if($('.boxes p a').length){
$(".boxes .box").click(function() {
window.open($(this).find("a").attr("href"));
return false;
});
}
});
The problem I'm running into is the click function gets applied to all divs instead of only those with links.
The desired behavior is to only create a fully clickable div only when an anchor element is found.
For the purposes of this use case, the div (.box) is generated dynamically and wrapping the element in an anchor tag (<div> </div>) is not possible.
Fiddle: https://jsfiddle.net/fu8xLg0d/

Because you add event listeners on all the .boxes .box classes, which are all your divs.
Just add something like :
$(".boxes .box").has('a')...
to narrow it to those only containing an a element
JSFiddle

use .parent to solve your purpose:
$(document).ready(function() {
if($('.boxes p a').length){
$("a").parent().parent().click(function() {
window.open($(this).find("a").attr("href"));
return false;
});
}
});
But yes, it can even create a problem so i will say to give a class to your link and then call its parent... :)

Plotisateur just beat me by a minute or two! :P
if($('.boxes p a').length){
$(".boxes .box").has('a').click(function() {
window.open($(this).find("a").attr("href"));
return false;
});
Here's the code anyway: https://jsfiddle.net/fu8xLg0d/1/

You can try this.
$(document).ready(function() {
var anchorbox =$(".boxes p a");
if(anchorbox.length>0){
$(anchorbox).parent().click(function() {
window.open($(this).find("a").attr("href"));
return false;
});
}
});

div (.box) is generated dynamically.
Delegate the click event from the body to the target div and on click on the element check if it has anchor tag. For adding the pointer icon create a separate function which will add the icon to the div only if it has an anchor tag as child
$(document).ready(function() {
// separate function to add pointer only if a is present
addClassToElem();
$("body").on('click', '.box', function() {
if ($(this).find('a').length) {
window.open($(this).find("a").attr("href"));
return false;
}
})
});
function addClassToElem() {
$('.box a').each(function(a, b) {
$(this).parent().addClass('linkIcon')
})
}
.linkIcon {
cursor: pointer;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="boxes">
<div class="box">
<p>Some text with a link</p>
</div>
<div class="box">
<p>Some text without a link</p>
</div>
<div class="box">
<p>Some text with a link</p>
</div>
<div class="box">
<p>Some text without a link</p>
</div>
</div>

This little change, helps you to resolve the issue.
$(document).ready(function() {
if($('.boxes p a').length){
$(".boxes .box").click(function() {
if ($(this).children('p').children('a').length) {
window.open($(this).find("a").attr("href"));
return false;
}
});
}
});
the difference from your code is, additionally add a checking
if ($(this).children('p').children('a').length) {
window.open($(this).find("a").attr("href"));
return false;
}

Testing if a click is in a div and all its children

I am facing an issue about this.
<div id="1">
<div id="2">
</div>
<div id="3">
<div id="4">
</div>
</div>
</div>
<div id="others_div">
</div>
I want to add the class "hidden" to "1" when I click on something which is not "1" nor one of its children.
Now I am using this but I have a lack of imagination for solving this issue...
document.onclick = function(e)
{
if(e.target.id!="1")
{
$("#1").addClass("hidden");
}
}

Well, to avoid e.stopPropagation() (maybe you want that event to bubble up to some other ancestor) You can check if it is not clicked on #1 nor on it's children like this:
$('body').on('click', function(e) {
if (!((e.target.id== "1") || $(e.target).closest('#1').length)) {
$("#1").addClass("hidden");
}
});

You could use a jQuery check like the following one to check if the current element is your 1 element or traverse the DOM to see if the current target is contained within an element with an ID of 1 :
<script>
$(function(){
// Trigger this when something is clicked
$(document).click(function(e){
// Toggle the hidden class based on if the current element is 1
// or if it is contained in an element with ID of 1
$("#1").toggleClass('hidden',!((e.target.id== "1") || $(e.target).closest('#1').length))
});
});
</script>
Generally, you should avoid using ID attributes that only consists of numbers as they are not valid (ID attributes must begin with a letter). Ignoring this could result in some issues with regards to CSS or jQuery selection.

JQuery
$('body').on( "click", function(e) {
if(e.target.id !== "1")
{
$("#1").addClass("hidden");
}
});

I think you want this
// taken from http://stackoverflow.com/questions/152975/how-to-detect-a-click-outside-an-element
$('html').click(function() {
//Hide the menus if visible
alert('hide');
});
$('#one').click(function(event){
event.stopPropagation();
});
div#one {
background: yellow;
}
div#others_div {
background: green;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<div id="one">
div one
<div id="2">
div two
</div>
<div id="3">
div three
<div id="4">
div four
</div>
</div>
</div>
<div id="others_div">
other div
</div>

How to add slide animation when showing elements

I would like to add animation effect to following code when showing tree items.
I know that jquery has slide functions, and css has "transition", but not sure how to apply these to my code. Any ideas?
<head>
<script language="JavaScript">
function show(){
var elements = document.getElementsByClassName("label");
for(var i = 0, length = elements.length; i < length; i++) {
elements[i].style.display = 'block';
}
}
</script>
<style>
.label {
-webkit-padding-start: 20px;
display: none;
}
</style>
</head>
<body>
<div>
<div onclick="show()">1st Row</div>
<div>
<div class="label">First</div>
<div class="label">Second</div>
<div class="label">Third</div>
</div>
<div>2nd Row</div>
</div>
</body>

If you are planning to use jQuery then you can use slideDown and slideUp method to show/hide elements with animation. There is slideToggle method which alternatively show/hides the element with animcation. You can modify your show method as below
Working demo
function show(obj){
var $this = $(obj);//Here obj points to the element clicked
//Now you have to show/hide the next sibling of the element clicked
//We will use next() method which gives the next sibling of element
//And then call slideToggle on it to show/hide alternatively
$this.next().slideToggle();
}
Change in the markup
<div onclick="show(this)">1st Row</div>

function show() {
$('.label').slideDown();
}
This selects all elements with the .label class and slides them into view. There is also a .fadeIn() function.
Also, you can attach click handlers by selectors (like an id or class):
<div>
<div class="row">1st Row</div>
<div>
<div class="label">First</div>
<div class="label">Second</div>
<div class="label">Third</div>
</div>
<div class="row">2nd Row</div>
</div>
Notice I removed the onClick="" statement and added a class to the row div. Then you can select the element you want to attach the click event to and keep all the code in one place:
$('.row').bind('click', function () {
$(this).next().find('.label').slideToggle();
});
This JavaScript above adds a click handler to all elements with the row class and toggles the display of all of the elements with the label class in the next element.
Here is a jsfiddle: http://jsfiddle.net/L34g3/.