Why JavaScript didint see that id visibility is set to hidden - javascript

Hi I whant that some element in my page appears only when a check box is selected, and disappears when it is not.
So I have this HTML:
<td><input type="checkbox" onchange="test('f1')"> Is selected?</td>
<div id="f1">some content</div>
And JavaScript:
function test(id) {
if (document.getElementById(id).style.visibility === "hidden") {
document.getElementById(id).style.visibility = "visible";
} else {
document.getElementById(id).style.visibility = "hidden";
}
}
And CSS:
#f1 {visibility: hidden;}
Right now it is working but not perfect, because the first select is always hidden.

As Juhana stated in the comments, the answer you're looking, which is explained perfectly in the link - is that: .style.* only looks at inline elements, quote:
"The element.style property lets you know only the CSS properties that were defined as inline in that element (programmatically, or defined in the style attribute of the element), you should get the computed style."
If you tweak your function a little bit to check if .style.visibility hasn't been set yet (thus ''), it'll toggle it upon first click.
function changeVisiblity() {
if ( getContent.style.visibility == "hidden" || getContent.style.visibility == '' ) {
getContent.style.visibility = "visible";
} else {
getContent.style.visibility = "hidden";
}
}
Secondly, try to teach yourself to keep away from onclick within HTML elements, as this makes it much harder to maintain the future.
var getCheckbox = document.getElementById("testcheckbox"),
getContent = document.getElementById("f1");
getCheckbox.addEventListener( 'change', changeVisiblity, null );
Demo Fiddle: http://jsfiddle.net/4yfWD/

Related

Changing properties of all <hr> html elements

In css I have set all the <hr> elements in my html to "display:none;" which works.
I have an onclick event listener set up to change the "display" to "block".
I use:
document.getElementsByTagName("hr").innerHTML.style.display = "block";
I get an error "Cannot read property 'style' of undefined".
Do it the following way:
var hrItems = document.getElementsByTagName("hr");
for(var i = 0; i < hrItems.length; i++) {
hrItems[i].style.display = 'block';
}
This is incorrect in two ways
getElementsByTagName gives you a list on elements and there is no method to operate on all elements, so you'll have to loop through all of them and add the required style individually.
innerHTML returns a string containing the mark up in an element but <hr> doesn't have any thing in it and the style property is on the <hr> itself.
var hrs = document.getElementsByTagName("hr");
for(var i = 0; i < hrs.length; i++) {
hrs[i].style.display = 'block';
}
Simple (and very effective) solution:
tag your body with a class-element
<body class="no_hr"> <article><hr/> TEXT Foo</article> <hr/> </body>
in css don't hide hr directly, but do
.no_hr hr {
display:none;
}
now define a second style in your css
.block_hr hr{
display:block;
}
in your buttons onClick, change the one and only body class from no_hr to block_hr
onclick() {
if ( document.body.className == "no_hr" ) {
document.body.className = "block_hr";
} else {
document.body.className = "no_hr";
}
}
This is a very charming solution, because you don't have to iterate over elements yourself, but let your browsers optimized procedures do their job.
For people who want a solution that doesn't require JavaScript.
Create an invisible checkbox at the top of the document and make sure that people can click on it.
<input type="checkbox" id="ruler"/>
<label for="ruler">Click to show or hide the rules</label>
Then tell the stylesheet that the <hr>s should be hidden by default, but should be visible if the checkbox is checked.
#ruler, hr {display:none}
#ruler:checked ~ hr {display:block}
Done. See fiddle.
getElementsByTagName() returns a node list, and therefore you must iterate through all the results. Additionally, there is no innerHTML property of an <hr> tag, and the style must be set directly on the tag.
I like writing these types of iterations using Array.forEach() and call:
[].forEach.call(document.getElementsByTagName("hr"), function(item) {
item.style.display = "block";
});
Or, make it even easier on yourself and use jQuery:
$("hr").show();

Detect position and hide a element

I'm trying to hide a button while a div have style positioned as 0.
The whole JS code to explain is:
$('#left-button').click(function() {
event.preventDefault();
$('#myTab').animate({
left: "+=200px"
}, "fast");
});
The code above WORKS. If I click on the button (left-button), the "mytab" div goes to the left. Now, I want to hide the #left-button, when the #myTab has style "left:0".
I tried this:
if ($('#myTab').css('left') == '0') {
$('#left-button').style.display = "none";
}
The basic style is
#myTab { width:300px; height:300px; position:relative; left:0; background:#777 }
#left-button {width:200px; height:200px; background:#ccc; }
There's no debug errors but nothing happens. What can I do?
If there's another method instead Js, let me know too.
Thank you very much.
http://jsfiddle.net/SgMDa/
You were just missing the unit value px
if ($('#myTab').css('left') == '0px') {
$('#left-button').hide();
}
And use .hide() instead style.display = "none";
Working Fiddle
The main problem in your code is with the line $('#left-button').style.display = "none"; and you have missed 'px' in the if condition if ($('#myTab').css('left') == '0') {
The if should be if ($('#myTab').css('left') == '0px') {
$ object returns jQuery wrapped array / object, what you are trying to access is the actual DOM element, so you have two options to access DOM element:
1. Using jQuery method hide()
$('#left-button').hide();
or
2. Using DOM property display
$('#left-button')[0].style.display = "none";
NOTE:
The jQuery Object: The Wrapped Set: Selectors return a jQuery object
known as the "wrapped set," which is an array-like structure that
contains all the selected DOM elements. You can iterate over the
wrapped set like an array or access individual elements via the
indexer ($(sel)[0] for example). More importantly, you can also apply
jQuery functions against all the selected elements.
Official information about jQuery Object
I think it is like you are getting value from left, try using the offset function
if ($('#myTab').offset().left == 0) {
$('#left-button').hide();
}
.css gives you measurement in px so you should try :
if ($('#myTab').css('left') == '0px') {
$('#left-button').style.display = "none";
}

Check if div only contains inline elements

I am trying to run a function that executes if a div only contains inline elements
I am not sure how to go about this short of having to list out every single block element and checking that the div doesn't contain that.
$(this).children().each(function(){
if(this.nodeName.toLowerCase() == 'p' || this.nodeName.toLowerCase() == 'h1' etc...){
check = true; //it contains block element so it is not only inline elements
return false;
}
});
Is there a better way?
Edit
To help clarify, I have a content editable div and the problem is that the user can delete all the block elements out of the div. I need to check this and add a block element to the div.
Check to see if those elements are actually block-level, as CSS can change their behavior completely:
var has_inline = $('#parent').children().filter(function() {
return $(this).css('display') !== 'block';
}).length > 0;
I'm not sure what you consider inline-block to be, so I'll just assume it behaves like an inline element for your purposes.
Demo: http://jsfiddle.net/hXckq/2/
How about has() in jQuery:
if ($(this).has("p,h1, ...")) { ... }
You could put the inline elements into a hash, then use in or hasOwnProperty:
var inline = {
"span": true,
"a": true,
...
};
if(this.nodeName.toLowerCase() in inline) {
}
Maybe try this, check if the css property of each element is indeed inline, this should work though I did not test this syntax may be incorrect:
$(this).children().each(function(){
if($(this).css('display', 'inline') == true){
return true;
}else{
return false;
}
}

change div/link class onclick with js - problems

Figured out how to change the class of a div/link/whatever onclick with JS. Here's a quick demo: http://nerdi.net/classchangetest.html
Now what I'm trying to figure out is how I can revert the previously clicked link to it's old class (or "deactivate") when clicking a new link.
Any ideas? Thanks!
function changeCssClass(navlink)
{
var links=document.getElementsByTagName('a');
for(var i=0, n=links.length; i<n; i++)
{
links[i].className='redText';
}
document.getElementById(navlink).className = 'blueText';
}
With this code all links will be red and lust clicked will be blue.
I hope it will be helpfull.
function changeCssClass(ele, add_class) {
// if add_class is not passed, revert
// to old className (if present)
if (typeof add_class == 'undefined') {
ele.className = typeof ele._prevClassName != 'undefined' ? ele._prevClassName : '';
} else {
ele._prevClassName = ele.className || '';
ele.className = add_class;
}
}
Try it here: http://jsfiddle.net/Zn7BL/
Use it:
// add "withClass"
changeCssClass(document.getElementById('test'), 'withClass');
// revert to original
changeCssClass(document.getElementById('test'));
It is a much better to post your code here, it makes it easier for those reading the question and for others searching later. Linked examples are unreliable and likely won't persist for long.
Copying from the link (and formatting for posting):
<style type="text/css">
.redText, .blueText { font-family: Arial; }
.redText { color : red; }
.blueText { color : blue; }
</style>
<script language="javascript" type="text/javascript">
The language attribute has been deprecated for a very long time, it should not be used. The type attribute is required, so keep that.
function changeCssClass(navlink)
The HTML class attribute is not sepecifically for CSS, it is used to group elements. A better name might be changeClassName.
{
if(document.getElementById(navlink).className=='redText')
{
document.getElementById(navlink).className = 'blueText';
}
else
{
document.getElementById(navlink).className = 'redText';
}
}
</script>
Link 1<br><br>
When called, the function associated with an inline listener will have its this keyword set to the element, so you can call the function as:
<a ... onclick="changeCssClass(this);" ...>
Then you don't have to pass the ID and you don't need getElementById in the function.
You might consider a function that "toggles" the class: adding it if it's not present, or removed if it is. You'll need to write some small functions like hasClass, addClass and removeClass, then your listener can be:
function toggleClass(el, className) {
if (hasClass(el, className) {
removeClass(el, className);
} else {
addClass(el, className);
}
}
Then give your links a default style using a style rule (i.e. apply the redText style to all links), then just add and remove the blueText class.
You might also consider putting a single function on a parent of the links to handle clicks from A elements — i.e. event delegation.

How do I check if an element is hidden in jQuery?

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());
}

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