I'm trying to understand addEventListener and using the mouseover ablity to hide a paragraph when someone hovers over a button. I am not getting any errors in the chrome developer so I am not sure what I am missing. What am I missing?
document.addEventListener("mouseover", myFunction);
document.addEventListener("mouseover", myThirdFunction);
function myFunction() {
document.getElementById("sun").style.visibility = "hidden";
}
function myThirdFunction() {
document.getElementById("sun").style.visibility = "visible";
}
<!-- You should:1. Rover over the below button and make the paragraph below
it disappear. -->
<input type="button" value="Roll Over Me" class="rollOverMe" />
<p id="sun"> This paragraph will burn from the heat of the sun!</p>
I'm expecting to see that whenever the user mouse hovers over the button that the p id="sun" is not visible.
Don't repeat document.getElementByIds in your page too much. It is okay for small apps - for practicing and for learning. Too many references/pickups from the DOM slows down performance.
As mentioned, try giving meaningful function names.
There are multiple mouse event listeners. To achieve what you are expecting, we need to use mouseleave and mouseover together.
var buttonElement = document.getElementById("tooltip-btn");
var paragraph = document.getElementById("sun");
function myFunction() {
paragraph.style.visibility = "hidden";
}
function myThirdFunction() {
paragraph.style.visibility = "visible";
}
buttonElement.addEventListener("mouseover", myFunction);
buttonElement.addEventListener("mouseleave", myThirdFunction);
<input id="tooltip-btn" type="button" value="Roll Over Me" class="rollOverMe" />
<p id="sun"> This paragraph will burn from the heat of the sun!</p>
Pretty simple issue and as you are starting out, I hope this helps.
Personally, I would stop using W3School and start using MDN. The MDN Tutorials are a good start.
As to your issue, there was a fair bit wrong. Something like the following is a basic structure for a lot of common scenarios.
function paraHide(e) {
var d = document.getElementById("sun");
d.style.visibility = "hidden";
}
function paraShow(e) {
var d = document.getElementById("sun");
d.style.visibility = "visible";
}
/*
window.onload means wait until the HTML has loaded, then
automatically start the following JavaScript
*/
window.onload = function() {
// get all elements with the class "rollOverMe"
var d = document.querySelectorAll(".rollOverMe");
// if any elements found, continue
if (d) {
var i, max = d.length;
// for each found element, add the following
// Event Lsiteners
for(i=0;i<max;i++) {
d[i].addEventListener("mouseover",paraHide,false)
d[i].addEventListener("mouseout",paraShow,false)
}
}
}
<input type="button" value="Roll Over Me" class="rollOverMe" />
<p id="sun"> This paragraph will burn from the heat of the sun!</p>
<input type="button" value="Over me too!" class="rollOverMe" />
Related
example..
<input type="button" value="click me" id="p1">
<script>
document.querySelector("#p1").onclick = function () {
this.style.backgroundColor = "green";
alert(`My background color is ${this.style.backgroundColor} ??`);
}
</script>
The alert write My background color is green but at the moment of alert the color is gray!!
I know many ways to get around this:
don't use alert but show a div..
use setTimeout
use sleep function with async await (What is the JavaScript version of sleep()?)
..but is a way to be sure that the browser rendering is done?
You could use requestAnimationFrame - similar to setTimeout except the browser will take care of the timing as the function is run before a repaint.
A simple example:
function tellMe() {
alert(`My background color is ${document.querySelector('#p1').style.backgroundColor} ??`);
}
document.querySelector("#p1").onclick = function() {
this.style.backgroundColor = "green";
requestAnimationFrame(function() {
requestAnimationFrame(tellMe)
});
}
<input type="button" value="click me" id="p1">
I am trying to write a tutorial for my students, in the form of a webpage with hidden "spoilers" that the student can unhide, presumably after thinking about the answer. So, long story short, the behavior I am looking for is:
in the beginning, the text appears with a lot of hidden words;
when a piece of text is clicked, it appears, and stays uncovered afterwards;
this should work with minimal overhead (not forcing me to install a complex framework) and on all my students' machines, even if the browser is outdated, even if jquery is not installed.
I searched for off the shelf solutions, but all those I checked were either too complicated or not doing exactly what I wanted. So I decided to do my own.
What I have so far is this:
<HTML>
<STYLE>
span.spoil {background-color: black;}
span.spoiled {background-color: white;}
</STYLE>
<HEAD>
<TITLE>SPOIL</TITLE>
<META http-equiv="Content-Type" content="text/html;charset=UTF-8">
<!--LINK rel="Stylesheet" type="text/css" href=".css"-->
</HEAD>
<BODY>
This is a text with <span class="spoil" onclick="showspoil(this)">spoil data</span>.
<br>
<span class="spoil" onclick="showspoil(this)">Unspoil me.</span>
<br>
<span class="spoil" onclick="showspoil(this)">And me.</span>
<script>
function showspoil(e) {
e.className="spoiled";
}
// var classname = document.getElementsByClassName("spoil");
// for (var i = 0; i < classname.length; i++) {
// classname[i].addEventListener('click', showspoil(WHATEXACTLY?), false);
// }
</script>
</BODY>
</HTML>
It does the job, except that I find it annoying to have to write explicitly the "onclick..." for each element. So I tried adding an event listener to each member of the class, by imitating similar resources found on the web: unfortunately, this part (the commented code above) does not work. In particular, I do not see which parameter I should pass to the function to transmit "the element itself".
Can anyone help? If I may play it lazy, I am more looking for an answer to this specific query than for pointers to a series of courses I should take: I admit it, I have not been doing html for a loooooong time, and I am sure I would need a lot of readings to be efficient again: simply, I do not have the time for the moment, and I do not really need it: I just need to solve this issue to set up a working solution.
Problem here is you are calling the method and assigning what it returns to be bound as the event listener
classname[i].addEventListener('click', showspoil(WHATEXACTLY?), false);
You can either use a closure or call the element directly.
classname[i].addEventListener('click', function () { showspoil(this); }, false);
or
classname[i].addEventListener('click', showspoil, false);
If you call it directly, you would need to change the function to
function showspoil(e) {
this.className="spoiled";
}
Another option would be to not bind click on every element, just use event delegation.
function showspoil(e) {
e.className="spoiled";
}
document.addEventListener("click", function (e) { //list for clcik on body
var clicked = e.target; //get what was clicked on
if (e.target.classList.contains("spoil")) { //see if it is an element with the class
e.target.classList.add("spoiled"); //if it is, add new class
}
});
.spoil { color: red }
.spoiled { color: green }
This is a text with <span class="spoil">spoil data</span>.
<br>
<span class="spoil">Unspoil me.</span>
<br>
<span class="spoil">And me.</span>
function unspoil() {
this.className = "spoiled"; // "this" is the clicked object
}
window.onload = function() {
var spoilers = document.querySelectorAll(".spoil"); // get all with class spoil
for (var i = 0; i < spoilers.length; i++) {
spoilers[i].onclick = unspoil;
}
}
span.spoil {
background-color: black;
}
span.spoiled {
background-color: white;
}
This is a text with <span class="spoil">spoil data</span>.
<br>
<span class="spoil">Unspoil me.</span>
<br>
<span class="spoil">And me.</span>
An additional approach could be to add the click-listener to the document and evaluate the event target:
document.addEventListener("click", function(e){
if (e.target.className == "spoil"){
e.target.className = "spoiled";
}
});
That way
you only need one event listener in the whole page
you can also append other elements dynamically with that class without the need for a new event handler
This should work, because the event's target is always the actual element being clicked. If you have sub-elements in your "spoil" items, you may need to traverse up the parent chain. But anyway I think this is the least resource-wasting way.
var spoilers = document.getElementsByClassName('spoil');
for(i=0;i<spoilers.length;i++){
spoilers[i].addEventListener('click',function(){
this.className = "spoiled";
});
}
Hey guys I have searched for many answers and none of them seem to be working so I am going to put my code here and hopefully you can help me figure this out.
I am going to have two buttons. The first button (show_Chappie) is going to show the hidden contents and another button (hide_Chappie) and hides it self when clicked.
The second button (hide_chappie) is going to hide the contents and bring back the first button (show_chappie). The hide_chappie button itself would also be hidden.
The information div is already hidden from the start. I did this on the CSS using the display:none;
Here's my HTML code so far:
<button class ="show_chappie" onclick="showInfo()">Show More</button>
<div class="info">Info here.</div>
<button class ="hide_chappie" onclick="hideInfo()">Show Less</button>
Here's my JavaScript code so far:
function showInfo(){
document.getElementById('chappie_info').style.display = "inline-block";
document.getElementById('show_chappie').style.display = "none";
document.getElementById('hide_chappie').style.display = "inline-block";
}
I haven't written the code for the hide_chappie button because I wanted to see this working first.
So where have I gone wrong here? Thanks for the help in advance.
You are trying to get the elements by id while they have a class, you should change the elements class to id like this:
<button id="show_chappie" onclick="showInfo()">Show More</button>
<div id="info">Info here.</div>
<button id="hide_chappie" onclick="hideInfo()">Show Less</button>
you should change your code to:
<button id ="show_chappie" onclick="showInfo()" >Show More</button>
<div class="info">Info here.</div>
<button id= "hide_chappie" onclick="showInfo()">Show Less</button>
if you want to use class here,you should change your Javascript Code to
function showInfo(){
document.getElementByClass('chappie_info')[0].style.display = "inline-block";
document.getElementByClass('show_chappie')[0].style.display = "none";
document.getElementByClass('hide_chappie')[0].style.display = "inline-block";
}
because function getElementsByClass returns a collection,so you should add [] to find out the result you want!
It's kind of annoying to turn all id's into classes, you can use:
function showInfo(){
document.getElementsByClassName('chappie_info').style.display = "inline-block";
document.getElementsByClassName('show_chappie').style.display = "none";
document.getElementsByClassName('hide_chappie').style.display = "inline-block";
}
This is supported by practically every browser these days so I wouldn't worry about that. If that is still an issue an you need to support ancient browsers, use this:
document.getElementsByClassName = function (a) {
var b = document.getElementsByTagName('*'), i, c=[];
for (i = 0; i < b.length; i += 1) { b[i].getAttribute('class')===a&&c.push(b[i]); }
return c;
};
Please check this page first : Solarking - About Us
Check first 2 boxes which has a READ MORE button. On clicking them, they expand a paragraph.
Now I want it to be like when I click on it, it should expand the text and change the button value to "CLOSE" from "READ MORE". And on again clicking on "CLOSE", it should change value to "READ MORE".
I searched for long time to see how to fire multiple events on onClick, but I saw that some said to use a ; in them, some said make a new function and put 2 functions in it.
Now I tried to make a new function with 2 functions inside it (one to expand the paragraph, other to change value of button, but I failed. (I am new to JS).
Help please. Thank you in advance!
Code I have on the page :
button code:
<p style="text-align: right;"><input id="button12" style="background-color: #eca200; color: #ffffff;" onclick="return toggleMe('para1')" type="button" value="Read more" /></p>
Script :
<script type="text/javascript">
function toggleMe(a){
var e=document.getElementById(a);
if(!e)return true;
if(e.style.display=="none"){
e.style.display="block"
}
else{
e.style.display="none"
}
return true;
}
</script>
I think the easiest way to do this would be to set a boolean variable. In other words, let's say that it starts off with the dclaration at the beginning of the page.
var hasbeenclicked = false;
Then, after the first click
hasbeenclicked = true;
After a second click
hasbeenclicked = false;
When the function is called, it checks the variable and operates accordingly. The following is not real JS....
if hasbeenclicked = true {
do some stuff;
}
else {
do some other stuff;
}
That is a simple way to accomplish what you are trying to do.
Additional info:
Use two DIV tags with separate ID's. One for the paragraph and one for the "label". Use getelementbyID to alter each one appropriately.
I noticed you are using jQuery.
You could use a toggle method.
Alter the html link. Add a class of expander and use the data attribute to identify the paragraph id
<p style="text-align: right;">
<input id="button12" data-toggle="para1" class="expander" style="background-color: #eca200; color: #ffffff;" type="button" value="Read more" />
</p>
The JS
$(".expander").click(function() {
var self = $(this);
$("#" + self.data('toggle')).slideToggle(500, function () {
if ($("#" + self.data('toggle')).is(':visible')) { // paragraph is open
self.val("Close");
} else { // paragraph is closed
self.val("Read More");
}
});
});
In Javascript, I'm trying to create a user script that will automatically click on a 'Blue Button'. Normally, I would do this:
var bluebutton = "document.getElementById("blue_button")"
if (bluebutton) {
bluebutton.onclick();
}
But NOW, the blue button does not have its own obvious ID. It's ID is randomized, and could be either button1, button2, or button3.
Here's the HTML that I'm talking about:
<div class="button_slot">
<div id="button1" style="cursor:pointer; padding-left:30px" onclick="buttonsubmit('button1')" onmouseover="infopane.display('Blue Button','I'm a blue button!')" onmouseout="infopane.clear()">
<div class="button_slot">
<div id="button2" style="cursor:pointer; padding-left:30px" onclick="buttonsubmit('button2')" onmouseover="infopane.display('Red Button','I'm a red button!')" onmouseout="infopane.clear()">
<div class="button_slot">
<div id="button3" style="cursor:pointer; padding-left:30px" onclick="buttonsubmit('button3')" onmouseover="infopane.display('Yellow Button','I'm a yellow button!')" onmouseout="infopane.clear()">
After a bit of reading, I've concluded that the only way to direct my onclick() to the correct element/string is by using ".toString().match(name)" as shown below:
function clickbutton(name) {
var button_list = document.querySelectorAll('.button_slot > div');
for (var i=0; i<button_list.length; i++) {
var button = button_list[i];
if (button.onmouseover && button.onmouseover.toString().match(name)) {
button.onmouseover();
button.onclick();
break;
}
}
}
clickbutton('Blue');
(note: sometimes I use clickbutton('Red'); or clickbutton('Yellow'); just to experiemen)
Now here's the problem. This method works so horribly... Sometimes, my script completely misses the button (as in, nothing gets clicked) EVEN THOUGH there is definitely a string with the word 'Blue' in it.
If someone could identify what I'm doing wrong, or perhaps even suggest a more effective method, I would appreciate it so much! Thank you!
First, I'm not sure why you can't give each button an ID which corresponds to it's color, because I believe that would be the easiest way to achieve this. But assuming that, for some reason, your button ID's must be randomized (or for that matter, maybe they don't even have an ID).
In this case, what I would do is give each button a data-button-type attribute, for instance:
<div data-button-type="Blue" id="..." style="..." onclick="..." onmouseover="..." onmouseout="...">
Now, I can check the attribute when looking for which button to click, for example:
function clickbutton(name) {
var button_list = document.querySelectorAll('.button_slot > div');
for (var i=0; i<button_list.length; i++) {
var button = button_list[i];
if (button.getAttribute('data-button-type') == name) {
button.onmouseover();
button.onclick();
break;
}
}
}
clickbutton('Blue');
I'm pretty sure you want to use indexOf although I think its most likely a timing issue.
First just try invoking it in a setTimeout function, so the document has (probably) loaded fully when you execute. It would explain it sometimes working sometimes not.
setTimeout(function(){ clickbutton(name) }, 3000);
I would do:
var clickButton = function(name){
var button_list = document.querySelectorAll('.button_slot > div');
for(var i = 0; i < button_list.length; i++){
var button = button_list[i];
if(button.getAttribute('onmouseover').indexOf(name) !== -1){
button.onclick.apply(); // They seem to have parameters in your example?
}
break;
}
}
setTimeout(function(){ clickButton('blah') }, 3000);
As a first attempt...