Develop Reference

Can't console.log() .style.display information

I'm able to correct switch between a dropdown menu being displayed and hidden when I click on my input tag, but when console logging the style displayed I get nothing shown on the console. What is the explanation for not being able to see this and how would I go about trying to correctly see which display style I used?
document.getElementById('search').addEventListener("click", function () {
const grid1 = document.querySelector(".modal");
grid1.style.display = grid1.style.display ? "none" : "flex";
console.log(grid1.style.display);
});

Instead of using 'yourelement.style.display' use 'getComputedStyle' function to get the value of any property in this case 'display', thats because Computed style contains all the CSS properties set to an element. Even if do not set a property to an element. You will still find that property in the computed styles.
Modifiying your code with 'getComputerStyle'
document.getElementById('search').addEventListener("click", function () {
const grid1=document.querySelector(".modal")
console.log(window.getComputedStyle(grid1).display)
grid1.style.display = window.getComputedStyle(grid1).display == "none" ? "flex" : "none";
console.log(window.getComputedStyle(grid1).display)
})
.modal {
display: none;
}
<input id="search">
<select class="modal"></select>
For more clarification check Window.getComputedStyle() in MDN Web Docs

Inner DIV CSS style updation with Javascript

For the following styles, how does one change the value of background color using javascript.
i)Internal Style sheet and/or ii) External Style sheet
I am using the card deck slide show from https://github.com/dynamicdriverepo/carddeckslideshow
div.stackcontainer > div.inner{
background: #D7F9FF; }

One way would be to use a CSS variable (Only available in the latest browsers)
div.stackcontainer > div.inner{ background: var(--inner-bg-color, #D7F9FF); }
Then you can use JS to set the value for --inner-bg-color anywhere from div.inner or above.
document.querySelector('div.stackcontainer').style.setProperty('--inner-bg-color', 'red')
But if you can't change their CSS then you need to adjust the style for that element:
var el = document.querySelector('div.stackcontainer > div.inner');
if (el) {
el.style.backgroundColor = '#FF0000';
}
Be aware that you are now messing with the specificity values that determine what CSS to use. And, if you want to reset to the original then you need to remove the style value from that element.
var el = document.querySelector('div.stackcontainer > div.inner');
if (el) {
el.style.backgroundColor = '';
}

Get CSS property from a dynamically added element [duplicate]

How do I toggle the visibility of an element using .hide(), .show(), or .toggle()?
How do I test if an element is visible or hidden?

Since the question refers to a single element, this code might be more suitable:
// Checks CSS content for display:[none|block], ignores visibility:[true|false]
$(element).is(":visible");
// The same works with hidden
$(element).is(":hidden");
It is the same as twernt's suggestion, but applied to a single element; and it matches the algorithm recommended in the jQuery FAQ.
We use jQuery's is() to check the selected element with another element, selector or any jQuery object. This method traverses along the DOM elements to find a match, which satisfies the passed parameter. It will return true if there is a match, otherwise return false.

You can use the hidden selector:
// Matches all elements that are hidden
$('element:hidden')
And the visible selector:
// Matches all elements that are visible
$('element:visible')

if ( $(element).css('display') == 'none' || $(element).css("visibility") == "hidden"){
// 'element' is hidden
}
The above method does not consider the visibility of the parent. To consider the parent as well, you should use .is(":hidden") or .is(":visible").
For example,
<div id="div1" style="display:none">
<div id="div2" style="display:block">Div2</div>
</div>
The above method will consider div2 visible while :visible not. But the above might be useful in many cases, especially when you need to find if there is any error divs visible in the hidden parent because in such conditions :visible will not work.

None of these answers address what I understand to be the question, which is what I was searching for, "How do I handle items that have visibility: hidden?". Neither :visible nor :hidden will handle this, as they are both looking for display per the documentation. As far as I could determine, there is no selector to handle CSS visibility. Here is how I resolved it (standard jQuery selectors, there may be a more condensed syntax):
$(".item").each(function() {
if ($(this).css("visibility") == "hidden") {
// handle non visible state
} else {
// handle visible state
}
});

From How do I determine the state of a toggled element?
You can determine whether an element is collapsed or not by using the :visible and :hidden selectors.
var isVisible = $('#myDiv').is(':visible');
var isHidden = $('#myDiv').is(':hidden');
If you're simply acting on an element based on its visibility, you can just include :visible or :hidden in the selector expression. For example:
$('#myDiv:visible').animate({left: '+=200px'}, 'slow');

Often when checking if something is visible or not, you are going to go right ahead immediately and do something else with it. jQuery chaining makes this easy.
So if you have a selector and you want to perform some action on it only if is visible or hidden, you can use filter(":visible") or filter(":hidden") followed by chaining it with the action you want to take.
So instead of an if statement, like this:
if ($('#btnUpdate').is(":visible"))
{
$('#btnUpdate').animate({ width: "toggle" }); // Hide button
}
Or more efficient, but even uglier:
var button = $('#btnUpdate');
if (button.is(":visible"))
{
button.animate({ width: "toggle" }); // Hide button
}
You can do it all in one line:
$('#btnUpdate').filter(":visible").animate({ width: "toggle" });

The :visible selector according to the jQuery documentation:
They have a CSS display value of none.
They are form elements with type="hidden".
Their width and height are explicitly set to 0.
An ancestor element is hidden, so the element is not shown on the page.
Elements with visibility: hidden or opacity: 0 are considered to be visible, since they still consume space in the layout.
This is useful in some cases and useless in others, because if you want to check if the element is visible (display != none), ignoring the parents visibility, you will find that doing .css("display") == 'none' is not only faster, but will also return the visibility check correctly.
If you want to check visibility instead of display, you should use: .css("visibility") == "hidden".
Also take into consideration the additional jQuery notes:
Because :visible is a jQuery extension and not part of the CSS specification, queries using :visible cannot take advantage of the performance boost provided by the native DOM querySelectorAll() method. To achieve the best performance when using :visible to select elements, first select the elements using a pure CSS selector, then use .filter(":visible").
Also, if you are concerned about performance, you should check Now you see me… show/hide performance (2010-05-04). And use other methods to show and hide elements.

How element visibility and jQuery works;
An element could be hidden with display:none, visibility:hidden or opacity:0. The difference between those methods:
display:none hides the element, and it does not take up any space;
visibility:hidden hides the element, but it still takes up space in the layout;
opacity:0 hides the element as "visibility:hidden", and it still takes up space in the layout; the only difference is that opacity lets one to make an element partly transparent;
if ($('.target').is(':hidden')) {
$('.target').show();
} else {
$('.target').hide();
}
if ($('.target').is(':visible')) {
$('.target').hide();
} else {
$('.target').show();
}
if ($('.target-visibility').css('visibility') == 'hidden') {
$('.target-visibility').css({
visibility: "visible",
display: ""
});
} else {
$('.target-visibility').css({
visibility: "hidden",
display: ""
});
}
if ($('.target-visibility').css('opacity') == "0") {
$('.target-visibility').css({
opacity: "1",
display: ""
});
} else {
$('.target-visibility').css({
opacity: "0",
display: ""
});
}
Useful jQuery toggle methods:
$('.click').click(function() {
$('.target').toggle();
});
$('.click').click(function() {
$('.target').slideToggle();
});
$('.click').click(function() {
$('.target').fadeToggle();
});

This works for me, and I am using show() and hide() to make my div hidden/visible:
if( $(this).css('display') == 'none' ){
/* your code goes here */
} else {
/* alternate logic */
}

You can also do this using plain JavaScript:
function isRendered(domObj) {
if ((domObj.nodeType != 1) || (domObj == document.body)) {
return true;
}
if (domObj.currentStyle && domObj.currentStyle["display"] != "none" && domObj.currentStyle["visibility"] != "hidden") {
return isRendered(domObj.parentNode);
} else if (window.getComputedStyle) {
var cs = document.defaultView.getComputedStyle(domObj, null);
if (cs.getPropertyValue("display") != "none" && cs.getPropertyValue("visibility") != "hidden") {
return isRendered(domObj.parentNode);
}
}
return false;
}
Notes:
Works everywhere
Works for nested elements
Works for CSS and inline styles
Doesn't require a framework

I would use CSS class .hide { display: none!important; }.
For hiding/showing, I call .addClass("hide")/.removeClass("hide"). For checking visibility, I use .hasClass("hide").
It's a simple and clear way to check/hide/show elements, if you don't plan to use .toggle() or .animate() methods.

Demo Link
$('#clickme').click(function() {
$('#book').toggle('slow', function() {
// Animation complete.
alert($('#book').is(":visible")); //<--- TRUE if Visible False if Hidden
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="clickme">
Click here
</div>
<img id="book" src="https://upload.wikimedia.org/wikipedia/commons/8/87/Google_Chrome_icon_%282011%29.png" alt="" width="300"/>
Source (from my blog):
Blogger Plug n Play - jQuery Tools and Widgets: How to See if Element is hidden or Visible Using jQuery

ebdiv should be set to style="display:none;". It works for both show and hide:
$(document).ready(function(){
$("#eb").click(function(){
$("#ebdiv").toggle();
});
});

One can simply use the hidden or visible attribute, like:
$('element:hidden')
$('element:visible')
Or you can simplify the same with is as follows.
$(element).is(":visible")

Another answer you should put into consideration is if you are hiding an element, you should use jQuery, but instead of actually hiding it, you remove the whole element, but you copy its HTML content and the tag itself into a jQuery variable, and then all you need to do is test if there is such a tag on the screen, using the normal if (!$('#thetagname').length).

When testing an element against :hidden selector in jQuery it should be considered that an absolute positioned element may be recognized as hidden although their child elements are visible.
This seems somewhat counter-intuitive in the first place – though having a closer look at the jQuery documentation gives the relevant information:
Elements can be considered hidden for several reasons: [...] Their width and height are explicitly set to 0. [...]
So this actually makes sense in regards to the box-model and the computed style for the element. Even if width and height are not set explicitly to 0 they may be set implicitly.
Have a look at the following example:
console.log($('.foo').is(':hidden')); // true
console.log($('.bar').is(':hidden')); // false
.foo {
position: absolute;
left: 10px;
top: 10px;
background: #ff0000;
}
.bar {
position: absolute;
left: 10px;
top: 10px;
width: 20px;
height: 20px;
background: #0000ff;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="foo">
<div class="bar"></div>
</div>
Update for jQuery 3.x:
With jQuery 3 the described behavior will change! Elements will be considered visible if they have any layout boxes, including those of zero width and/or height.
JSFiddle with jQuery 3.0.0-alpha1:
http://jsfiddle.net/pM2q3/7/
The same JavaScript code will then have this output:
console.log($('.foo').is(':hidden')); // false
console.log($('.bar').is(':hidden')); // false

expect($("#message_div").css("display")).toBe("none");

$(document).ready(function() {
if ($("#checkme:hidden").length) {
console.log('Hidden');
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="checkme" class="product" style="display:none">
<span class="itemlist"><!-- Shows Results for Fish --></span> Category:Fish
<br>Product: Salmon Atlantic
<br>Specie: Salmo salar
<br>Form: Steaks
</div>

To check if it is not visible I use !:
if ( !$('#book').is(':visible')) {
alert('#book is not visible')
}
Or the following is also the sam, saving the jQuery selector in a variable to have better performance when you need it multiple times:
var $book = $('#book')
if(!$book.is(':visible')) {
alert('#book is not visible')
}

Use class toggling, not style editing . . .
Using classes designated for "hiding" elements is easy and also one of the most efficient methods. Toggling a class 'hidden' with a Display style of 'none' will perform faster than editing that style directly. I explained some of this pretty thoroughly in Stack Overflow question Turning two elements visible/hidden in the same div.
JavaScript Best Practices and Optimization
Here is a truly enlightening video of a Google Tech Talk by Google front-end engineer Nicholas Zakas:
Speed Up Your Javascript (YouTube)

After all, none of examples suits me, so I wrote my own.
Tests (no support of Internet Explorer filter:alpha):
a) Check if the document is not hidden
b) Check if an element has zero width / height / opacity or display:none / visibility:hidden in inline styles
c) Check if the center (also because it is faster than testing every pixel / corner) of element is not hidden by other element (and all ancestors, example: overflow:hidden / scroll / one element over another) or screen edges
d) Check if an element has zero width / height / opacity or display:none / visibility:hidden in computed styles (among all ancestors)
Tested on
Android 4.4 (Native browser/Chrome/Firefox), Firefox (Windows/Mac), Chrome (Windows/Mac), Opera (Windows Presto/Mac WebKit), Internet Explorer (Internet Explorer 5-11 document modes + Internet Explorer 8 on a virtual machine), and Safari (Windows/Mac/iOS).
var is_visible = (function () {
var x = window.pageXOffset ? window.pageXOffset + window.innerWidth - 1 : 0,
y = window.pageYOffset ? window.pageYOffset + window.innerHeight - 1 : 0,
relative = !!((!x && !y) || !document.elementFromPoint(x, y));
function inside(child, parent) {
while(child){
if (child === parent) return true;
child = child.parentNode;
}
return false;
};
return function (elem) {
if (
document.hidden ||
elem.offsetWidth==0 ||
elem.offsetHeight==0 ||
elem.style.visibility=='hidden' ||
elem.style.display=='none' ||
elem.style.opacity===0
) return false;
var rect = elem.getBoundingClientRect();
if (relative) {
if (!inside(document.elementFromPoint(rect.left + elem.offsetWidth/2, rect.top + elem.offsetHeight/2),elem)) return false;
} else if (
!inside(document.elementFromPoint(rect.left + elem.offsetWidth/2 + window.pageXOffset, rect.top + elem.offsetHeight/2 + window.pageYOffset), elem) ||
(
rect.top + elem.offsetHeight/2 < 0 ||
rect.left + elem.offsetWidth/2 < 0 ||
rect.bottom - elem.offsetHeight/2 > (window.innerHeight || document.documentElement.clientHeight) ||
rect.right - elem.offsetWidth/2 > (window.innerWidth || document.documentElement.clientWidth)
)
) return false;
if (window.getComputedStyle || elem.currentStyle) {
var el = elem,
comp = null;
while (el) {
if (el === document) {break;} else if(!el.parentNode) return false;
comp = window.getComputedStyle ? window.getComputedStyle(el, null) : el.currentStyle;
if (comp && (comp.visibility=='hidden' || comp.display == 'none' || (typeof comp.opacity !=='undefined' && comp.opacity != 1))) return false;
el = el.parentNode;
}
}
return true;
}
})();
How to use:
is_visible(elem) // boolean

Example of using the visible check for adblocker is activated:
$(document).ready(function(){
if(!$("#ablockercheck").is(":visible"))
$("#ablockermsg").text("Please disable adblocker.").show();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="ad-placement" id="ablockercheck"></div>
<div id="ablockermsg" style="display: none"></div>
"ablockercheck" is a ID which adblocker blocks. So checking it if it is visible you are able to detect if adblocker is turned On.

$(document).ready(function() {
var visible = $('#tElement').is(':visible');
if(visible) {
alert("visible");
// Code
}
else
{
alert("hidden");
}
});
<script src="https://code.jquery.com/jquery-1.10.2.js"></script>
<input type="text" id="tElement" style="display:block;">Firstname</input>

You need to check both... Display as well as visibility:
if ($(this).css("display") == "none" || $(this).css("visibility") == "hidden") {
// The element is not visible
} else {
// The element is visible
}
If we check for $(this).is(":visible"), jQuery checks for both the things automatically.

Simply check visibility by checking for a boolean value, like:
if (this.hidden === false) {
// Your code
}
I used this code for each function. Otherwise you can use is(':visible') for checking the visibility of an element.

Because Elements with visibility: hidden or opacity: 0 are considered visible, since they still consume space in the layout (as described for jQuery :visible Selector) - we can check if element is really visible in this way:
function isElementReallyHidden (el) {
return $(el).is(":hidden") || $(el).css("visibility") == "hidden" || $(el).css('opacity') == 0;
}
var booElementReallyShowed = !isElementReallyHidden(someEl);
$(someEl).parents().each(function () {
if (isElementReallyHidden(this)) {
booElementReallyShowed = false;
}
});

But what if the element's CSS is like the following?
.element{
position: absolute;left:-9999;
}
So this answer to Stack Overflow question How to check if an element is off-screen should also be considered.

A function can be created in order to check for visibility/display attributes in order to gauge whether the element is shown in the UI or not.
function checkUIElementVisible(element) {
return ((element.css('display') !== 'none') && (element.css('visibility') !== 'hidden'));
}
Working Fiddle

Also here's a ternary conditional expression to check the state of the element and then to toggle it:
$('someElement').on('click', function(){ $('elementToToggle').is(':visible') ? $('elementToToggle').hide('slow') : $('elementToToggle').show('slow'); });

if($('#postcode_div').is(':visible')) {
if($('#postcode_text').val()=='') {
$('#spanPost').text('\u00a0');
} else {
$('#spanPost').text($('#postcode_text').val());
}

jQuery, selecting just number from id like "article-23"

All right, I have a div tag which got a class="blog-post" and id like id="article-23" (where "23" could be any number, as it is id of blog post in a database). I need to somehow get just a number from that id and than apply some rules to that div tag. So say:
if number from id % 2 == 0 {
set text colour black to associated div tag with class of blog-post
} else {
set text colour white to associated div tag with class of blog-post
}
Thats just a "pseudo" code to show logic that I wan't to apply dependent if number from id is even or odd, but the question remains same, how do I just get number from id like "article-23" ?

As simple as
var number = "article-23".match(/\d+/)[0];
But you have to be sure that any digit exists in the string, otherwise you'd get a error.

You can actually apply rules via function, which makes this the cleanest solution (in my opinion):
$(".blog-post").css('color', function () {
return +this.id.replace('article-', '') % 2 ? 'blue' : 'red';
});
http://jsfiddle.net/ExplosionPIlls/Jrc5u/

Try this:
$('.blog-post[id^="article-"]').each(function () {
if (parseInt(this.id.replace('article-', '')) % 2 === 0) {
$('#' + this.id).css('color', 'black');
} else {
$('#' + this.id).css('color', 'white');
}
});
jsFiddle Demo

As an alternative, HTML5 supports these things called "data attributes", which are specifically meant for attaching data to your DOM without abusing things like the "class" or "id" attributes. jQuery provides a handy .data method for reading these attributes in a more obvious way.
You can add your own numeric ID attribute using something like "data-id":
<div class="blog-post" data-id="23" />
$("#blog-post").each(function () {
console.log($(this).data("id")); // Look up the data-id attribute
});

If I'm understanding correctly, you want the number after the hyphen of the id tag of your .blog-post class.
var article = $(".blog-post").attr('id'); //get the id
var article = article.split("-"); // split it on hyphens
return article = article[article.length-1]; // return the last element

Javascript only recognizising inline style and not style set in head

I have simple JS function that toggles the DISPLAY of a DIV. The DIV display is set to 'none' by default. If I use an inline style to set the display, it works fine, but if I set the style in the head it only works after I run the function the second time. So it only sees that the display is set to none after the display is set in the function. It doesn't recognize that it is set in the CSS in the head. If I use an inline style, it works fine.
Also, if I change my conditional statement from:
if (OBJ.style.display == 'none')
to
if (OBJ.style.display = 'none')

Use window.getCurrentStyle or element.currentStyle in order to obtain style from the head or body. They're supported by different browsers so here's a cross-browser example:
function getStyle( elem, style ) {
var a = window.getComputedStyle,
b = elem.currentStyle;
if ( a ) return a( elem ).getPropertyValue( style );
else if ( b ) return b[ style ];
}
getStyle( document.getElementById('OBJ'), 'display' )

The style property of an element only contains the inline style, not inherited styles or styles from a style sheet.
You can use the offsetHeight property to check if the element has any size, as it is zero when the element is not visible.
if (OBJ.offsetHeight == 0) ...

Another suggestion is to use css classes:
css:
.hide{
display:none;
}
html:
<div id="mydiv" class="hide">hello world</div>
<button onclick="toggle();">toggle</button>
js:
function toggle(){
var obj = document.getElementById('mydiv');
if(obj.className == 'hide')
obj.className = '';
else
obj.className = 'hide'
}
http://jsfiddle.net/XBhMA/1/
Note this will only work if the element contains only one class. If it contains more, you will need to modify.