how to check the event handlers' properties in js? - javascript

<!DOCTYPE HTML>
<html>
<body>
<style type="text/css">
#a {background-color:blue;width:100px;height:200px;}
#b {background-color:red;margin-left:25px;width:50px;height:100px;}
</style>
<div id="a">a
<div id="b">b</div>
</div>
<script>
document.getElementById("a").onclick = function() {console.log("A is clicked");}
document.getElementById("b").onclick = function() {console.log("B is clicked");}
document.onclick = function() {console.log("Document is clicked");}
</script>
</body>
</html>
Question:
For above codes, it registered 3 click events handlers, they are also objects, right? if so, how could I check these 3 handlers/objects' properties, methods in console?

When you do
document.getElementById("a").onclick = function() {console.log("A is clicked");}
you are just assigning a function to that anchors onclick property, then when that anchor is clicked, the browser will fire that function. If you want to read what this function is, you just need to output
console.log(document.getElementById("a").onclick);

I'm really not sure what you are trying to do, maybe this helps you:
document.getElementById("a").onclick = function(event) {
console.log("A is clicked");
console.log(this); //refers to the source element object
console.log(event); //refers to the event object
}

Related

How to pass click location to a function as parameter in JS? [duplicate]

so in my html i have this portion:
<body ondblclick="myfunc();">
<div id="id1">dasd</div>
<div id="id2">dasda</div>
</body>
and in javascript the function is :
function myfunc() {
do stuff here...
}
i want to know inside myfunc() on which element of the html body the doubleclick was made, because i don't want to triger myfunc() on every doubleclicked element
so how can i detect the id of the element doubleclicked?
<body ondblclick="myfunc(event);">
function myfunc(e) {
// e.target -> element that was clicked
}
make your HTML as
<body ondblclick="myfunc(event);">
and make myfunc as:
function myfunc(event) {
alert(event.target.id); //here you can get element id that is double clicked
event.stopPropagation();
}
<!doctype html>
<html>
<head>
<meta charset=utf-8>
<title>ondblclick event example</title>
<script>
function initElement() {
var body = document.getElementById("bdy");
body.ondblclick = showAlert;
}
function showAlert(e){
alert(e.target.id);
}
window.onload = initElement;
</script>
</head>
<body id="bdy">
<div id="id1">dasd</div>
<div id="id2">dasda</div>
</body>
</html>
you can define different events with use of on or bind suppose..
$("#id").on("doubleClick",function () {} );
so it will know that its double click event..
or for javascript you can use like this
<body ondblclick="myfunc(event);">
function myfunc(event) {
do something..
}

Is there something like a clicked===true conditional statment in javascript?

using javascript, is there a condition something like this
if (clicked===true && var===3) {
function executes here
}
if there isn't, how can you get the same effect?
For mouse and UI handling the Javascript model is based on events. In other words what you do is
element.onclick = function() {
// what to do when that element is clicked
};
for example:
<!DOCTYPE html>
<html>
<body>
<div id="thediv">Click me</div>
<script>
document.getElementById("thediv").onclick = function() {
alert("Awww... why did you do that?");
};
</script>
</body>
</html>
you have to bind an eventhandler to the element. you can do this inline with an onclick eventhandler. Also you can't use the name var because it is a reserved word in javascript.
html
<a id="mylink" href="#" onclick="handleMyClick();">Click me</a>
javascript
var myvar=3;
handleMyClick(){
if(myvar==3){
alert("you clicked the link and myvar is 3");
}
}

Onclick button doesn't function

i try to create a button when the page is load.
<!DOCTYPE html>
<html>
<head>
<script>
function createButton(){
var newButton = document.createElement("button");
newButton.onclick="document.write('Tasto premuto')";
var textButton = document.createTextNode("Premi qui");
newButton.appendChild(textButton);
document.body.appendChild(newButton);
}
</script>
</head>
<body onload="createButton()">
</body>
</html>
the button is created succesfully, but the function that I have associated with onClick event doesn't work. any ideas?
onclick expects a function, not a string:
newButton.onclick = function() { document.write('Tasto premuto') };
Please see this jsFiddle
Of course, you should be aware that document.write() completely clears the DOM of all current content, rather than simply appending the string to the existing content.
You're assigning a string to function pointer:
Change:
newButton.onclick="document.write('Tasto premuto')";
To:
newButton.onclick= function(){ document.write('Tasto premuto') };

Javascript Dynamic Event Handling, Not Jquery

here is my code
<html>
<head>
<script type="text/javascript">
window.onload = function(){
sel = document.getElementsByTagName('select');
for(i=0;i<sel.length;i++)sel[i].onclick = function(){alert('');}
}
</script>
</head>
<body>
<div id="ss"></div>
<select></select>
<input type="button" onclick="document.getElementById('ss').appendChild(document.createElement('select'))"/>
</body>
</html>
"onclick" event working for static tag "Select" but not working for Dynamically created "Select". In other word i want to know what is alternate to .live of JQuery in Javascript.
Bind the event to a parent element, that already exists in the DOM:
document.body.addEventListener('click', function (e) {
if (e.target.tagName.toLowerCase() == 'select') {
alert('You clicked a select!');
}
});
JS Fiddle demo.
It would be slightly more sensible to bind the click to an element 'closer' to the form, and if you use getElementById() rather than getElementByTagName() it's more simple, since you don't have to worry about the index of the number you're binding to.
jQuery's live function works by using "Event Delegation". The basic idea is that you bind a listener on a parent element, which is guaranteed to exist when the page loads. Any element below that (with the exception of some) will fire off an event which can be caught by the parent listener. From there you would need to retrieve the target/sourceElement of the event and determine whether or not it's one you care about.
Something like this will work for listening to clicks. Just make sure that any new elements you are adding are located within the proper parent container and have an attribute which distinguishes them from the rest of the clickable elements.
<html>
<head>
<script type="text/javascript">
window.onload = function(){
// get the relevant container
var eventContainer = document.getElementById("EventContainer");
// bind a click listener to that container
eventContainer.onclick = function(e){
// get the event
e = e || window.event;
// get the target
var target = e.target || e.srcElement;
// should we listen to the click on this element?
if(target.getAttribute("rel") == 'click-listen')
{
alert("You clicked something you are listening to!");
}// if
};
};
</script>
</head>
<body>
<div id="EventContainer">
<input type="button" rel="click-listen" name="myButton" value="Listening to this button." />
<input type="button" name="anotherButton" value="Not listening." />
<p>I'm also listening to this a element: listening to this</p>
</div>
</body>
</html>
there's no need to bind the onclick handler to every select every time you add one.
I am not going to retype your whole page, but you'll see what's going on by reading following snippets:
function handler() {
alert('You clicked a select!');
}
window.onload = function(){
sel = document.getElementsByTagName('select');
for(int i= 0; i < sel.length; i++) {
sel[i].onclick = handler;
}
}
function addSelect() {
var slt = document.createElement("select");
document.getElementById('ss').appendChild(slt);
slt.onclick = handler;
}
<input type="button" onclick="addSelect();"/>
You're only setting the onclick when the window loads. All you need to do is put the code currently in the window.onload into a named function, then call it every time you add a new select.
here's the dumb way to do it:
<html>
<head>
<script type="text/javascript">
function update () {
sel = document.getElementsByTagName('select');
for(i=0;i<sel.length;i++)sel[i].onclick = function(){alert('');}
}
window.onload = update;
</script>
</head>
<body>
<div id="ss"></div>
<select></select>
<input type="button" onclick="document.getElementById('ss').appendChild(document.createElement('select'));update();"/>
</body>
</html>
You can use a cross-browser solution as shown below to add event handler dynamically
sel = document.getElementsByTagName('select');
for( i=0; i<sel.length; i++){
if (sel[i].addEventListener){
sel[i].addEventListener("click", clickHandler, false);
} else if (sel[i].attachEvent){
sel[i].attachEvent("onclick", clickHandler);
}else{
sel[i].onclick = clickHandler;
}
}
function clickHandler(event){
}

How to get the element that fired the "onclick" event

<script>
function clicky(e){
console.log(e) //the clicked element
}
</script>
<span onClick="clicky(this)">Clickable</span>
In the script above, the console.log(e) will give me the <span> that I clicked on.
Is there any way that I could omit the clicky(this) and still get the element?
It's because I don't want to put (this) all over the document.
Any answer are welcomed.
See this:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Test</title>
</head>
<body>
<div id="foo" style="background:blue; width:100px; height:100px">
<script>
function clicky(e){
console.log(e);
}
var foo = document.getElementById("foo");
foo.onclick = function(e){clicky((e || window.event).target);}
</script>
</body>
</html>
You could try this, not tested though.
var spans = document.getElementsByTagName('span');
spans.attachEvent('click'.'clicky');
function clicky(e){
console.log(e) //the clicked element
}
or
var spans = document.getElementsByTagName('span');
for (i in spans)
{
spans[i].attachEvent('click'.'clicky');
}
function clicky(e){
console.log(e) //the clicked element
}
function clicky(e, elem){
<span onClick="clicky(event, this)">Clickable</span>
Or you could use Prototype or jQuery or any other library. I would improve your life.

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