Determine which element the mouse pointer is on top of in JavaScript - javascript

I want a function that tells me which element the mouse cursor is over.
So, for example, if the user's mouse is over this textarea (with id wmd-input), calling window.which_element_is_the_mouse_on() will be functionally equivalent to $("#wmd-input").

DEMO
There's a really cool function called document.elementFromPoint which does what it sounds like.
What we need is to find the x and y coords of the mouse and then call it using those values:
document.addEventListener('mousemove', e => {
console.clear()
console.log( document.elementFromPoint(e.clientX, e.clientY) )
}, {passive: true})
[class^='level']{
width: 100px;
height: 100px;
padding: 15px;
background: #00000033;
}
<div class='level-1'>
<div class='level-2'>
<div class='level-3'>
Hover
</div>
</div>
</div>
document.elementFromPoint
jQuery event object

In newer browsers, you could do the following:
document.querySelectorAll( ":hover" );
That'll give you a NodeList of items that the mouse is currently over in document order. The last element in the NodeList is the most specific, each preceding one should be a parent, grandparent, and so on.

Although the following may not actually answering the question, since this is the first result of googling (the googler may not asking exactly the same question:), hope it will provide some extra input.
There are actually two different approaches to get a list of all elements the mouse is currently over (for newer browsers, perhaps):
The "structural" approach - Ascending DOM tree
As in dherman's answer, one can call
var elements = document.querySelectorAll(':hover');
However, this assumes that only children will overlay their ancestors, which is usually the case, but not true in general, especially when dealing with SVG where element in different branches of the DOM tree may overlap each other.
The "visual" approach - Based on "visual" overlapping
This method uses document.elementFromPoint(x, y) to find the topmost element, temporarily hide it (since we recover it immediately in the same context, the browser will not actually renders this), then go on to find the second topmost element... Looks a little hacky, but it returns what you expect when there are, e.g., siblings elements in a tree occluding each other. Please find this post for more details,
function allElementsFromPoint(x, y) {
var element, elements = [];
var old_visibility = [];
while (true) {
element = document.elementFromPoint(x, y);
if (!element || element === document.documentElement) {
break;
}
elements.push(element);
old_visibility.push(element.style.visibility);
element.style.visibility = 'hidden'; // Temporarily hide the element (without changing the layout)
}
for (var k = 0; k < elements.length; k++) {
elements[k].style.visibility = old_visibility[k];
}
elements.reverse();
return elements;
}
Try both, and check their different returns.

elementFromPoint() gets only the first element in DOM tree. This is mostly not enough for developers needs. To get more than one element at e.g. the current mouse pointer position, this is the function you need:
document.elementsFromPoint(x, y) . // Mind the 's' in elements
This returns an array of all element objects under the given point.
Just pass the mouse X and Y values to this function.
More information is here: DocumentOrShadowRoot.elementsFromPoint()
For very old browsers which are not supported, you may use this answer as a fallback.

The following code will help you to get the element of the mouse pointer. The resulted elements will display in the console.
document.addEventListener('mousemove', function(e) {
console.log(document.elementFromPoint(e.pageX, e.pageY));
})

Mouseover events bubble, so you can put a single listener on the body and wait for them to bubble up, then grab the event.target or event.srcElement:
function getTarget(event) {
var el = event.target || event.srcElement;
return el.nodeType == 1? el : el.parentNode;
}
<body onmouseover="doSomething(getTarget(event));">

You can look at the target of the mouseover event on some suitable ancestor:
var currentElement = null;
document.addEventListener('mouseover', function (e) {
currentElement = e.target;
});
Here’s a demo.

Demo :D
Move your mouse in the snippet window :D
<script>
document.addEventListener('mouseover', function (e) {
console.log ("You are in ", e.target.tagName);
});
</script>

<!-- One simple solution to your problem could be like this: -->
<div>
<input type="text" id="fname" onmousemove="javascript: alert(this.id);" />
<!-- OR -->
<input type="text" id="fname" onclick="javascript: alert(this.id);" />
</div>
<!-- Both mousemove over the field & click on the field displays "fname"-->
<!-- Works fantastic in IE, FireFox, Chrome, Opera. -->
<!-- I didn't test it for Safari. -->

You can use this selector to undermouse object and then manipulate it as a jQuery object:
$(':hover').last();

2022 Update:
document.elementsFromPoint() (Note the 's' in elements) is compatible with all major browsers. It basically does the same thing that elementFrompoint does, but retrieves all the elements in DOM order.
Mozilla has a good example of this:
HTML
<div>
<p>Some text</p>
</div>
<p>Elements at point 30, 20:</p>
<div id="output"></div>
JavaScript
let output = document.getElementById("output");
if (document.elementsFromPoint) {
let elements = document.elementsFromPoint(30, 20);
for (var i = 0; i < elements.length; i++) {
output.textContent += elements[i].localName;
if (i < elements.length - 1) {
output.textContent += " < ";
}
}
} else {
output.innerHTML = "<span style=\"color: red;\">" +
"Browser does not support <code>document.elementsFromPoint()</code>" +
"</span>";
}
Output
Some text
Elements at point 30, 20:
p < div < body < html
https://developer.mozilla.org/en-US/docs/Web/API/Document/elementsFromPoint

The target of the mousemove DOM event is the top-most DOM element under the cursor when the mouse moves:
(function(){
//Don't fire multiple times in a row for the same element
var prevTarget=null;
document.addEventListener('mousemove', function(e) {
//This will be the top-most DOM element under cursor
var target=e.target;
if(target!==prevTarget){
console.log(target);
prevTarget=target;
}
});
})();
This is similar to #Philip Walton's solution, but doesn't require jQuery or a setInterval.

Here's a solution for those that may still be struggling. You want to add a mouseover event on the 'parent' element of the child element(s) you want detected. The below code shows you how to go about it.
const wrapper = document.getElementById('wrapper') //parent element
const position = document.getElementById("displaySelection")
wrapper.addEventListener('mousemove', function(e) {
let elementPointed = document.elementFromPoint(e.clientX, e.clientY)
console.log(elementPointed)
});
Demo on CodePen

Let me start out by saying that I don't recommend using the method I'm about to suggest. It's much better to use event driven development and bind events only to the elements you're interested in knowing whether or not the mouse is over with mouseover, mouseout, mouseenter, mouseleave, etc.
If you absolutely must have the ability to know which element the mouse is over, you'd need to write a function that binds the mouseover event to everything in the DOM, and then store whatever the current element is in some variable.
You could so something like this:
window.which_element_is_the_mouse_on = (function() {
var currentElement;
$("body *").on('mouseover', function(e) {
if(e.target === e.currentTarget) {
currentElement = this;
}
});
return function() {
console.log(currentElement);
}
}());
Basically, I've created an immediate function which sets the event on all elements and stores the current element within the closure to minimize your footprint.
Here's a working demo that calls window.which_element_is_the_mouse_on every second and logs what element the mouse is currently over to the console.
http://jsfiddle.net/LWFpJ/1/

Related

Change color of all elements in class on click JavaScript

I have an image (SVG) of a human body. I would like to use JavaScript so that when I click a particular area (say, the lower leg) then all of the elements with the class "lower-leg" (even if not clicked) have their color changed -- this makes it much easier for the user.
Here is the JavaScript I currently have:
function changeclassstyle() {
var c = document.getElementsByClassName("lower-leg");
for (var i=0; i<c.length; i++) {
c[i].style.fill = "red";
}
}
The problem with this code is that it is only generalized for "lower-leg". I may have over a dozen classes I would like this to work for and don't think it is efficient to write 12 functions with the only change being the class name. Is there a way to grab what class was selected and then input that in the function?
--
Additionally, I would love to figure out how, once that section of the body is selected, I can store the class name. I would, in the end, want to store the selection, along with other inputted information in a database. But, this may be for a future question unless someone can help!
Here's how I would do it (tested on a couple of div's).
What we're doing is passing the event object to the event handler (your changeclassstyle() function). It then uses the class of the clicked-on item (the event target's class) and changes everything else on that page with that same class name to use your new desired CSS style.
function changeclassstyle(e) {
// Get all items that have the same class as the item that was clicked
var limbs = document.getElementsByClassName(e.target.className); // for div's and the like
// var limbs = document.getElementsByClassName(e.target.className.baseVal); // turns out this is needed for SVG items
// "limbs" is an HTMLCollection, not an array, so functions like .foreach won't work; C-style for-loops or modern for/let/of loops are better
for (let item of limbs) {
item.style.backgroundColor = 'red';
// item.style.fill = 'red'; // This is probably what you need for your SVG items
}
// You could still use your C-style for loop if needed/wanted
/*
for (var i=0; i<limbs.length; i++) {
limbs[i].style.fill = "red";
}
*/
}
The onchange call looks like this (using my div as the example):
<div class="upper-arm" onclick="changeclassstyle(event)">
</div>
<div class="lower-leg" onclick="changeclassstyle(event)">
</div>
The whole example with simple div's.
<html>
<head><title>stuff</title></head>
<body>
<script type="text/javascript">
function changeclassstyle(e) {
// For debugging. You may want to expand 'e' here in your browser's debug tools if you're not seeing the values you need/want
console.log(e)
var limbs = document.getElementsByClassName(e.target.className.baseVal);
for (let item of limbs) {
item.style.backgroundColor = 'red';
}
}
</script>
<style type="text/css">
div {
height: 100px;
width: 100px;
background-color: 'white';
border: 1px solid black;
}
</style>
<div class="upper-arm" onclick="changeclassstyle(event)">
</div>
<div class="upper-arm" onclick="changeclassstyle(event)">
</div>
<div class="upper-arm" onclick="changeclassstyle(event)">
</div>
<div class="lower-leg" onclick="changeclassstyle(event)">
</div>
<div class="lower-leg" onclick="changeclassstyle(event)">
</div>
<div class="lower-leg" onclick="changeclassstyle(event)">
</div>
</body>
</html>
You can use parameters in function where you pass class and color like below
function changeStyle(cls,clr) {
let elems = document.getElementsByClassName(cls);
if(!elems) return;
for (let elem of elems) {
elem.style.color = clr;
}
}
As per the iteration of many classes like i said you can store classes in array and iterate each of them.
let classes = ['one','two','three','four'];
classes.forEach(function (cls) {
changeStyle(cls,"red");
});
You can play with fiddle here if you want to test/experiment: https://jsfiddle.net/thrL5uqw/8/
Note: Change style property as you wish, For now i have used color for demo
I'm a bit late to the party, but here's my take on the problem.
Like the others told you, you'll need to use an additional parameter to your function to specify the class you want to modify your elements (or try to figure out the class from the clicked element), therefore you should have something like that:
/**
* This function will handle the click event on one of the part of the SVG.
* #param {string} lClass This the class of the element to modify
*/
function handleClick(lClass) {
for (let e of document.getElementsByClassName(lClass)) {
// Here you can do all the changes you need on the SVG element.
e.style.fill = "red";
}
}
And when it comes to the event binding, you could do like the other suggested and add the onclick event binding propery on the HTML Element, or you could bind it in you JS with the addEventListener function (that way you don't have to repeat the onclick property on each of your SVG elements).
// For each element of all the listed class, bind the "click" event to the handleClick function
const listenClass = [/*List of your classes*/];
for (let l of listenClass) {
for (let e of document.getElementsByClassName(l)) {
e.addEventListener('click', handleClick.bind(this, l));
}
}
Demo: https://plnkr.co/edit/gay2yBaVi5QD868fsTa6?p=preview
I hope it helped.

getting the item under the cursor when the cursor is clicked in google chrome [duplicate]

I want a function that tells me which element the mouse cursor is over.
So, for example, if the user's mouse is over this textarea (with id wmd-input), calling window.which_element_is_the_mouse_on() will be functionally equivalent to $("#wmd-input").
DEMO
There's a really cool function called document.elementFromPoint which does what it sounds like.
What we need is to find the x and y coords of the mouse and then call it using those values:
document.addEventListener('mousemove', e => {
console.clear()
console.log( document.elementFromPoint(e.clientX, e.clientY) )
}, {passive: true})
[class^='level']{
width: 100px;
height: 100px;
padding: 15px;
background: #00000033;
}
<div class='level-1'>
<div class='level-2'>
<div class='level-3'>
Hover
</div>
</div>
</div>
document.elementFromPoint
jQuery event object
In newer browsers, you could do the following:
document.querySelectorAll( ":hover" );
That'll give you a NodeList of items that the mouse is currently over in document order. The last element in the NodeList is the most specific, each preceding one should be a parent, grandparent, and so on.
Although the following may not actually answering the question, since this is the first result of googling (the googler may not asking exactly the same question:), hope it will provide some extra input.
There are actually two different approaches to get a list of all elements the mouse is currently over (for newer browsers, perhaps):
The "structural" approach - Ascending DOM tree
As in dherman's answer, one can call
var elements = document.querySelectorAll(':hover');
However, this assumes that only children will overlay their ancestors, which is usually the case, but not true in general, especially when dealing with SVG where element in different branches of the DOM tree may overlap each other.
The "visual" approach - Based on "visual" overlapping
This method uses document.elementFromPoint(x, y) to find the topmost element, temporarily hide it (since we recover it immediately in the same context, the browser will not actually renders this), then go on to find the second topmost element... Looks a little hacky, but it returns what you expect when there are, e.g., siblings elements in a tree occluding each other. Please find this post for more details,
function allElementsFromPoint(x, y) {
var element, elements = [];
var old_visibility = [];
while (true) {
element = document.elementFromPoint(x, y);
if (!element || element === document.documentElement) {
break;
}
elements.push(element);
old_visibility.push(element.style.visibility);
element.style.visibility = 'hidden'; // Temporarily hide the element (without changing the layout)
}
for (var k = 0; k < elements.length; k++) {
elements[k].style.visibility = old_visibility[k];
}
elements.reverse();
return elements;
}
Try both, and check their different returns.
elementFromPoint() gets only the first element in DOM tree. This is mostly not enough for developers needs. To get more than one element at e.g. the current mouse pointer position, this is the function you need:
document.elementsFromPoint(x, y) . // Mind the 's' in elements
This returns an array of all element objects under the given point.
Just pass the mouse X and Y values to this function.
More information is here: DocumentOrShadowRoot.elementsFromPoint()
For very old browsers which are not supported, you may use this answer as a fallback.
The following code will help you to get the element of the mouse pointer. The resulted elements will display in the console.
document.addEventListener('mousemove', function(e) {
console.log(document.elementFromPoint(e.pageX, e.pageY));
})
Mouseover events bubble, so you can put a single listener on the body and wait for them to bubble up, then grab the event.target or event.srcElement:
function getTarget(event) {
var el = event.target || event.srcElement;
return el.nodeType == 1? el : el.parentNode;
}
<body onmouseover="doSomething(getTarget(event));">
You can look at the target of the mouseover event on some suitable ancestor:
var currentElement = null;
document.addEventListener('mouseover', function (e) {
currentElement = e.target;
});
Here’s a demo.
Demo :D
Move your mouse in the snippet window :D
<script>
document.addEventListener('mouseover', function (e) {
console.log ("You are in ", e.target.tagName);
});
</script>
<!-- One simple solution to your problem could be like this: -->
<div>
<input type="text" id="fname" onmousemove="javascript: alert(this.id);" />
<!-- OR -->
<input type="text" id="fname" onclick="javascript: alert(this.id);" />
</div>
<!-- Both mousemove over the field & click on the field displays "fname"-->
<!-- Works fantastic in IE, FireFox, Chrome, Opera. -->
<!-- I didn't test it for Safari. -->
You can use this selector to undermouse object and then manipulate it as a jQuery object:
$(':hover').last();
2022 Update:
document.elementsFromPoint() (Note the 's' in elements) is compatible with all major browsers. It basically does the same thing that elementFrompoint does, but retrieves all the elements in DOM order.
Mozilla has a good example of this:
HTML
<div>
<p>Some text</p>
</div>
<p>Elements at point 30, 20:</p>
<div id="output"></div>
JavaScript
let output = document.getElementById("output");
if (document.elementsFromPoint) {
let elements = document.elementsFromPoint(30, 20);
for (var i = 0; i < elements.length; i++) {
output.textContent += elements[i].localName;
if (i < elements.length - 1) {
output.textContent += " < ";
}
}
} else {
output.innerHTML = "<span style=\"color: red;\">" +
"Browser does not support <code>document.elementsFromPoint()</code>" +
"</span>";
}
Output
Some text
Elements at point 30, 20:
p < div < body < html
https://developer.mozilla.org/en-US/docs/Web/API/Document/elementsFromPoint
The target of the mousemove DOM event is the top-most DOM element under the cursor when the mouse moves:
(function(){
//Don't fire multiple times in a row for the same element
var prevTarget=null;
document.addEventListener('mousemove', function(e) {
//This will be the top-most DOM element under cursor
var target=e.target;
if(target!==prevTarget){
console.log(target);
prevTarget=target;
}
});
})();
This is similar to #Philip Walton's solution, but doesn't require jQuery or a setInterval.
Here's a solution for those that may still be struggling. You want to add a mouseover event on the 'parent' element of the child element(s) you want detected. The below code shows you how to go about it.
const wrapper = document.getElementById('wrapper') //parent element
const position = document.getElementById("displaySelection")
wrapper.addEventListener('mousemove', function(e) {
let elementPointed = document.elementFromPoint(e.clientX, e.clientY)
console.log(elementPointed)
});
Demo on CodePen
Let me start out by saying that I don't recommend using the method I'm about to suggest. It's much better to use event driven development and bind events only to the elements you're interested in knowing whether or not the mouse is over with mouseover, mouseout, mouseenter, mouseleave, etc.
If you absolutely must have the ability to know which element the mouse is over, you'd need to write a function that binds the mouseover event to everything in the DOM, and then store whatever the current element is in some variable.
You could so something like this:
window.which_element_is_the_mouse_on = (function() {
var currentElement;
$("body *").on('mouseover', function(e) {
if(e.target === e.currentTarget) {
currentElement = this;
}
});
return function() {
console.log(currentElement);
}
}());
Basically, I've created an immediate function which sets the event on all elements and stores the current element within the closure to minimize your footprint.
Here's a working demo that calls window.which_element_is_the_mouse_on every second and logs what element the mouse is currently over to the console.
http://jsfiddle.net/LWFpJ/1/

How to get DOM or jQuery element by mouse coordinates? [duplicate]

I want a function that tells me which element the mouse cursor is over.
So, for example, if the user's mouse is over this textarea (with id wmd-input), calling window.which_element_is_the_mouse_on() will be functionally equivalent to $("#wmd-input").
DEMO
There's a really cool function called document.elementFromPoint which does what it sounds like.
What we need is to find the x and y coords of the mouse and then call it using those values:
document.addEventListener('mousemove', e => {
console.clear()
console.log( document.elementFromPoint(e.clientX, e.clientY) )
}, {passive: true})
[class^='level']{
width: 100px;
height: 100px;
padding: 15px;
background: #00000033;
}
<div class='level-1'>
<div class='level-2'>
<div class='level-3'>
Hover
</div>
</div>
</div>
document.elementFromPoint
jQuery event object
In newer browsers, you could do the following:
document.querySelectorAll( ":hover" );
That'll give you a NodeList of items that the mouse is currently over in document order. The last element in the NodeList is the most specific, each preceding one should be a parent, grandparent, and so on.
Although the following may not actually answering the question, since this is the first result of googling (the googler may not asking exactly the same question:), hope it will provide some extra input.
There are actually two different approaches to get a list of all elements the mouse is currently over (for newer browsers, perhaps):
The "structural" approach - Ascending DOM tree
As in dherman's answer, one can call
var elements = document.querySelectorAll(':hover');
However, this assumes that only children will overlay their ancestors, which is usually the case, but not true in general, especially when dealing with SVG where element in different branches of the DOM tree may overlap each other.
The "visual" approach - Based on "visual" overlapping
This method uses document.elementFromPoint(x, y) to find the topmost element, temporarily hide it (since we recover it immediately in the same context, the browser will not actually renders this), then go on to find the second topmost element... Looks a little hacky, but it returns what you expect when there are, e.g., siblings elements in a tree occluding each other. Please find this post for more details,
function allElementsFromPoint(x, y) {
var element, elements = [];
var old_visibility = [];
while (true) {
element = document.elementFromPoint(x, y);
if (!element || element === document.documentElement) {
break;
}
elements.push(element);
old_visibility.push(element.style.visibility);
element.style.visibility = 'hidden'; // Temporarily hide the element (without changing the layout)
}
for (var k = 0; k < elements.length; k++) {
elements[k].style.visibility = old_visibility[k];
}
elements.reverse();
return elements;
}
Try both, and check their different returns.
elementFromPoint() gets only the first element in DOM tree. This is mostly not enough for developers needs. To get more than one element at e.g. the current mouse pointer position, this is the function you need:
document.elementsFromPoint(x, y) . // Mind the 's' in elements
This returns an array of all element objects under the given point.
Just pass the mouse X and Y values to this function.
More information is here: DocumentOrShadowRoot.elementsFromPoint()
For very old browsers which are not supported, you may use this answer as a fallback.
The following code will help you to get the element of the mouse pointer. The resulted elements will display in the console.
document.addEventListener('mousemove', function(e) {
console.log(document.elementFromPoint(e.pageX, e.pageY));
})
Mouseover events bubble, so you can put a single listener on the body and wait for them to bubble up, then grab the event.target or event.srcElement:
function getTarget(event) {
var el = event.target || event.srcElement;
return el.nodeType == 1? el : el.parentNode;
}
<body onmouseover="doSomething(getTarget(event));">
You can look at the target of the mouseover event on some suitable ancestor:
var currentElement = null;
document.addEventListener('mouseover', function (e) {
currentElement = e.target;
});
Here’s a demo.
Demo :D
Move your mouse in the snippet window :D
<script>
document.addEventListener('mouseover', function (e) {
console.log ("You are in ", e.target.tagName);
});
</script>
<!-- One simple solution to your problem could be like this: -->
<div>
<input type="text" id="fname" onmousemove="javascript: alert(this.id);" />
<!-- OR -->
<input type="text" id="fname" onclick="javascript: alert(this.id);" />
</div>
<!-- Both mousemove over the field & click on the field displays "fname"-->
<!-- Works fantastic in IE, FireFox, Chrome, Opera. -->
<!-- I didn't test it for Safari. -->
You can use this selector to undermouse object and then manipulate it as a jQuery object:
$(':hover').last();
2022 Update:
document.elementsFromPoint() (Note the 's' in elements) is compatible with all major browsers. It basically does the same thing that elementFrompoint does, but retrieves all the elements in DOM order.
Mozilla has a good example of this:
HTML
<div>
<p>Some text</p>
</div>
<p>Elements at point 30, 20:</p>
<div id="output"></div>
JavaScript
let output = document.getElementById("output");
if (document.elementsFromPoint) {
let elements = document.elementsFromPoint(30, 20);
for (var i = 0; i < elements.length; i++) {
output.textContent += elements[i].localName;
if (i < elements.length - 1) {
output.textContent += " < ";
}
}
} else {
output.innerHTML = "<span style=\"color: red;\">" +
"Browser does not support <code>document.elementsFromPoint()</code>" +
"</span>";
}
Output
Some text
Elements at point 30, 20:
p < div < body < html
https://developer.mozilla.org/en-US/docs/Web/API/Document/elementsFromPoint
The target of the mousemove DOM event is the top-most DOM element under the cursor when the mouse moves:
(function(){
//Don't fire multiple times in a row for the same element
var prevTarget=null;
document.addEventListener('mousemove', function(e) {
//This will be the top-most DOM element under cursor
var target=e.target;
if(target!==prevTarget){
console.log(target);
prevTarget=target;
}
});
})();
This is similar to #Philip Walton's solution, but doesn't require jQuery or a setInterval.
Here's a solution for those that may still be struggling. You want to add a mouseover event on the 'parent' element of the child element(s) you want detected. The below code shows you how to go about it.
const wrapper = document.getElementById('wrapper') //parent element
const position = document.getElementById("displaySelection")
wrapper.addEventListener('mousemove', function(e) {
let elementPointed = document.elementFromPoint(e.clientX, e.clientY)
console.log(elementPointed)
});
Demo on CodePen
Let me start out by saying that I don't recommend using the method I'm about to suggest. It's much better to use event driven development and bind events only to the elements you're interested in knowing whether or not the mouse is over with mouseover, mouseout, mouseenter, mouseleave, etc.
If you absolutely must have the ability to know which element the mouse is over, you'd need to write a function that binds the mouseover event to everything in the DOM, and then store whatever the current element is in some variable.
You could so something like this:
window.which_element_is_the_mouse_on = (function() {
var currentElement;
$("body *").on('mouseover', function(e) {
if(e.target === e.currentTarget) {
currentElement = this;
}
});
return function() {
console.log(currentElement);
}
}());
Basically, I've created an immediate function which sets the event on all elements and stores the current element within the closure to minimize your footprint.
Here's a working demo that calls window.which_element_is_the_mouse_on every second and logs what element the mouse is currently over to the console.
http://jsfiddle.net/LWFpJ/1/

Javascript how to make function work on other function

I've just started learn JavaScript and wanted to try something.
How can I make JavaScript function work on other function? Like, I want when you click on a div, other div will have background-color:yellow; (or x.style.backgroundColor="yellow"; in JS), like this:
<div onclick="yellow">Click me to paint the other div in yellow</div>
<div id="painted">I should be painted yellow if you click the above div!</div>
In C-language I know it can be possible if you call recursion so I tried use it though I don't know.
Of course it didn't succeed but there's a jsbin if you want to look.Q: How can I paint a div in yellow background with other div function using JavaScript?
Thanks in advance.
You will have to attach the function with parenthesis like fillYellow(),
<div onclick="fillYellow()">Click me to paint the other div in yellow</div>
<div id="painted">I should be painted yellow if you click the above div!</div>
<script>
function fillYellow(){
document.getElementById('painted').style.background = "yellow";
}
</script>
Inside this function get the painted div by it's id and apply background color for this div.
You should have document.getElementById("backgroundChange"); instead of getElementById("backgroundChange"); and it will work :)
As your question was "How can I make JavaScript function work on other function?" I started to think maybe you're really talking about doing something event-driven.
Therefore, why not consider this (slightly more advanced) solution
When you click a <div>, you fire a custom "paint" event at every <div>.
The event fired at itself is different to at other <div>s.
When a <div> node sees a "paint" event e, it applies e.style to node.style
The code would look like this
function paintEvent(style) { // function make a custom event
var ev = new Event('paint');
ev.style = style;
return ev;
}
function applyPaint(node, style) { // function to style a node
var key;
for (key in style) { // loop over object
node.style[key] = style[key];
}
}
function paintHandler(e) { // function to fire when you see a "paint" event
applyPaint(this, e.style);
}
function clickHandler(e) { // function to fire when you see a "click" event
var divs = document.getElementsByTagName('div'),
i,
paint = paintEvent({'background-color': 'yellow'});
this.dispatchEvent(paintEvent({'background-color': 'red'}));
for (i = 0; i < divs.length; ++i) { // loop over array-like
if (divs[i] !== this)
divs[i].dispatchEvent(paint);
}
}
window.addEventListener('load', function () { // when the Window has loaded
var divs = document.getElementsByTagName('div'),
i;
for (i = 0; i < divs.length; ++i) { // loop over array-like
divs[i].addEventListener('click', clickHandler); // attach the handlers
divs[i].addEventListener('paint', paintHandler);
}
});
DEMO
Your yellow event handler should look up the div with the id "painted" and then add a class to it which will give it yellow text.
This is one way ( a simple one) but where are a number of other similar ways to accomplish this.

Disable permanent active state

I have a link, and if you drag this link then release, the link will keep his active state.
Example: http://jsfiddle.net/Ek43k/3/
<a href="javascript:void(0);" id="foo" >Drag me</a>
#foo:active{
color:red;
}
How can I prevent this?
(Only in IE and FF)
This is a known bug in Firefox, see https://bugzilla.mozilla.org/show_bug.cgi?id=193321
The bug has had an on-and-off status with several reports; the behavior is non-standard and browser-specific.
You can build a work-around for it, but you're stuck with javascript. After much searching, I determined that unless you're running in privileged mode (i.e. your code is in an extension), you cannot directly influence the pseudo-selector states. That means you're left with adding/removing a class name:
<a href="#" onmousedown="this.className = '';" ondragend="this.className = 'inactive';" id="foo" >Drag me</a>
Try it: http://jsfiddle.net/frsRS/
If you do have privileged mode, you can use the method that Firebug employs in their CSS Panel, using inIDOMUtils.setContentState
var node = document.getElementById("foo");
var domUtil = Components.classes["#mozilla.org/inspector/dom-utils;1"].getService(Components.interfaces.inIDOMUtils);
domUtil.setContentState( node , 1);
Edit
Here is specific code for binding cross-browser delegates rather than putting the javascript inline (shown here for demonstration purposes, but generally bad practice)
function addEvent(ele, evnt, funct) {
if (ele.addEventListener) // W3C
return ele.addEventListener(evnt,funct,false);
else if (ele.attachEvent) // IE
return ele.attachEvent("on"+evnt,funct);
}
addEvent(document.body, 'mousedown', function (e) {
if(e.target.tagName == 'A') e.target.style.color = '';
});
addEvent(document.body, 'dragend', function (e) {
if(e.target.tagName == 'A') e.target.style.color = 'blue';
});
Try it: http://jsfiddle.net/HYJCQ/
This uses the element's style rather than a css class, you can swap out the methods as desired.
Another way, as suggested by Supr, is to remove and immediately re-add the element from DOM. You can accomplish this using a delegate as well:
function addEvent(ele, evnt, funct) {
if (ele.addEventListener) // W3C
return ele.addEventListener(evnt,funct,false);
else if (ele.attachEvent) // IE
return ele.attachEvent("on"+evnt,funct);
}
addEvent(document.body, 'dragend', function (e) {
if(e.target.tagName != 'A') return;
var parent = e.target.parentNode;
var sib = e.target.nextSibling;
parent.insertBefore(
parent.removeChild(e.target),
sib
);
});
Try it: http://jsfiddle.net/ymPfH/
Both methods that utilize delegation are better approaches than looping elements -- that way, the script will apply to any a tags added to the page after load (similar to how jQuery's live or on methods work).
Documentation
Bugzilla entry - https://bugzilla.mozilla.org/show_bug.cgi?id=193321
Drag and Drop on MDN (ondragend) - https://developer.mozilla.org/en-US/docs/Drag_and_Drop
inIDOMUtils - https://developer.mozilla.org/en-US/docs/XPCOM_Interface_Reference/inIDOMUtils
Detach and reattach the link from the DOM tree to disable its active state. Do this when the drag ends and you've got this:
$('a').on('dragend',function(){
var $this = $(this),
$parent = $this.parent(),
$next = $(this.nextSibling); // $.next() doesn't include text
$this.detach().insertBefore($next);
});
No need to mess with your HTML or CSS or do away with :active. Seems to work in both FF and IE.
Edit: I don't usually write pure Javascript for DOM-handling so the quality of this might not be top notch, but here it is without jQuery:
(function(){
var previousOnload = window.onload || function noop(){};
window.onload = function (){
// Call any previously added onload callbacks
previousOnload();
// Add deactivator to each <a> element
var elements = document.getElementsByTagName('a');
for (var i=0; i<elements.length; i++){
elements[i].ondragend = deactivate;
}
function deactivate(){
var parent = this.parentNode,
position = this.nextSibling;
parent.removeChild(this);
// Using insertBefore instead of appendChild so that it is put at the right position among the siblings
parent.insertBefore(this, position);
}
};
})();
I took care of a few issues that came to mind to make it fully plug-and-play. Tested in Opera, Chrome, Firefox and Internet Explorer.
Edit 2: Inspired by Chris, another way to apply the fix is to use the ondragend attribute directly to connect the deactivator (not tested):
<head>
<script>
function deactivate(){
var parent = this.parentNode,
position = this.nextSibling;
parent.removeChild(this);
// Using insertBefore instead of appendChild so that it is put at the right position among the siblings
parent.insertBefore(this, position);
}
</script>
</head>
<body>
Drag me
<body>
The downside is that it requires the ondragend attribute with javascript to be specified on each link manually/explicitly. I guess it's a matter of preference.
Final (?) Edit: See comments for delegate/live versions of these and Chris' answer.
If jQuery is an option, I think this code works, at least in FF: http://jsfiddle.net/Ek43k/89/
HTML
<a href="#" id="foo" class="inactive" >Drag me</a>
CSS
.inactive:active{color:red;}
.active:active{color:blue;}
jQuery
$('body').on('mousedown', 'a.inactive', function() {
$(this).on('mousemove', function() {
$(this).removeClass().addClass('active');
});
});
$('body').on('mousedown', 'a.active', function() {
$(this).removeClass().addClass('inactive');
});
just add this CSS:
#foo:hover {
color: green;
}

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