Develop Reference

I have to double click the follow button to functioning this is due to using click event 2 time

I am working on follow button and with the help of JavaScript I've come up with the following code.
But the problem is I have to double click the follow button to functioning this is due to using click event 2 time. I am open to better methods of solving this too.
var value = null;
const onClick = (event) => {
// event.target.id
value = event.target.id;
console.log(value);
document.getElementById(`${value}`).addEventListener('click',function(){
// console.log(value.id);
if(this.classList.contains('follow')){
this.classList.remove('follow');
this.innerHTML ="Following";
this.style.backgroundColor = 'green' ;
}else{
this.classList.add('follow');
this.style.backgroundColor = 'rgb(27,18,83)' ;
this.innerHTML="Follow";
}
})
}
window.addEventListener('click', onClick);

There is a double click event. You can check the if it satisfies your requirement.
MDN link - https://developer.mozilla.org/en-US/docs/Web/API/Element/dblclick_event

For multiple buttons with the same function, I would give all of them the same class (e.g. "btn"). Then in JS simply get all of the elements with this class, loop over the HTMLCollection which you would get and assign each element an eventlistener. When you want to change something on the button you have to use event.target in the function:
let buttons = document.getElementsByClassName("btn");
for (btn of buttons) {
btn.addEventListener("click", (event) => {
if(event.target.classList.contains('follow')){
event.target.classList.remove('follow');
event.target.innerHTML ="Following";
event.target.style.backgroundColor = 'green' ;
}else{
event.target.classList.add('follow');
event.target.style.backgroundColor = 'rgb(27,18,83)' ;
event.target.innerHTML="Follow";
}
});
}
<button class="btn">1</button>
<button class="btn">2</button>

Disabling a button in vanilla JavaScript and in jQuery

Vanilla JavaScript
In vanilla JavaScript, one can easily enable and disable a button using the following statement:
button.disabled = state;
This works both when humans try to click a button and when buttons are clicked programmatically:
var button = document.getElementById('myButton');
button.addEventListener('click', function() {
alert('world');
});
button.disabled = true;
button.click(); // No output
button.disabled = false;
button.click(); // Output : "Hello" and "world
button.disabled = true;
button.click(); // No output
<input type="button" id="myButton" value="button" onClick="alert('Hello')"/>
This also works when using the MouseEvent interface:
var button = document.getElementById('myButton');
var click = new MouseEvent("click", {
"view": window
});
button.addEventListener('click', function() {
alert('world');
});
button.disabled = true;
button.dispatchEvent(click); // No output
button.disabled = false;
button.dispatchEvent(click); // Output : "Hello" and "world
button.disabled = true;
button.dispatchEvent(click); // No output
<input type="button" id="myButton" value="button" onClick="alert('Hello')"/>
jQuery
I can't seem to be able to do the same with jQuery, though :
var button = $("#myButton");
button.on("click", function() {
alert("world");
});
button.prop("disabled", true);
button.click(); // Output : "world" and "Hello"
button.prop("disabled", false);
button.click(); // Output : "world" and "Hello"
button.prop("disabled", true);
button.click(); // Output : "world" and "Hello"
<script src="https://code.jquery.com/jquery-1.12.2.min.js"></script>
<input type="button" id="myButton" value="button" onClick="alert('Hello')"/>
Both button.prop("disabled", true); and button.attr("disabled", true); simply change the disabled property of the button element, but neither disables the actual click event. This means that events are triggered whenever button.click(); is called, even if the button is disabled!
Additionally, "world" and "Hello" are output in the wrong order.
The simplest code I could come up with to emulate the behavior of the vanilla JavaScript versions, is this :
var button = $("#myButton");
button.on("click", function() {
alert("world");
});
button.disable = (function() {
var onclick = null;
var click = [];
return function(state) {
if(state) {
this.prop('disabled', true);
if(this.prop('onclick') !== null) {
onclick = this.prop('onclick');
this.prop('onclick', null);
}
var listeners = $._data(this.get()[0], "events");
listeners = typeof listeners === 'undefined' ? [] : listeners['click'];
if(listeners && listeners.length > 0) {
for(var i = 0; i < listeners.length; i++) {
click.push(listeners[i].handler);
}
this.off('click');
}
} else {
this.removeProp('disabled');
if(onclick !== null) {
this.prop('onclick', onclick);
onclick = null;
}
if(click.length > 0) {
this.off('click');
for(var i = 0; i < click.length; i++) {
this.on("click", click[i]);
}
click = [];
}
}
}
})();
button.disable(true);
button.click(); // No output
button.disable(false);
button.click(); // Output : "Hello" and "world
button.disable(true);
button.click(); // No output
<script src="https://code.jquery.com/jquery-1.12.2.min.js"></script>
<input type="button" id="myButton" value="button" onClick="alert('Hello')"/>
That is, of course, ridiculously convoluted and "hacky" code to achieve something as simple as disabling a button.
My questions
Why is it that jQuery - unlike vanilla JS - doesn't disable the events when disabling a button?
Is this to be considered a bug or a feature in jQuery?
Is there something I'm overlooking?
Is there a simpler way to get the expected behavior in jQuery?

To achieve expected result, you can utilize .isTrigger within jQuery triggered click handler to determine if event is triggered by javascript, and not user action.
Define attribute event listener as a named function, where this can be passed to check disabled property at if condition if alert() is called, or not called.
Use .attr("disabled", "disabled") to set disabled at element, .removeAttr("disabled") to remove attribute; .attr("onclick", null) to remove event attribute onclick handler; .attr("onclick", "handleClick(true)") to reset event attribute.
<script src="https://code.jquery.com/jquery-3.1.0.js"></script>
<input type="button" id="myButton" value="button" onclick="handleClick(this)" />
<script>
function handleClick(el) {
if (el.disabled !== "disabled")
alert("Hello")
}
var button = $("#myButton");
button.on("click", function(e) {
console.log(e);
if (e.isTrigger !== 3 && !e.target.disabled)
alert("world");
});
button.attr("disabled", "disabled");
button.attr("onclick", null);
button.click(); // no output
setTimeout(function() {
button.removeAttr("disabled");
button.attr("onclick", "handleClick(button[0])");
button.click(); // Output : "world" and "Hello"
// click button during 9000 between `setTimeout` calls
// to call both jQuery event and event attribute
}, 1000);
setTimeout(function() {
button.attr("disabled", "disabled");
button.attr("onclick", null);
button.click(); // no output
}, 10000);
</script>

If you take a look to jquery-1.12.4.js at these lines:
handlers: function( event, handlers ) {
var i, matches, sel, handleObj,
handlerQueue = [],
delegateCount = handlers.delegateCount,
cur = event.target;
// Support (at least): Chrome, IE9
// Find delegate handlers
// Black-hole SVG <use> instance trees (#13180)
//
// Support: Firefox<=42+
// Avoid non-left-click in FF but don't block IE radio events (#3861, gh-2343)
if ( delegateCount && cur.nodeType &&
( event.type !== "click" || isNaN( event.button ) || event.button < 1 ) ) {
/* jshint eqeqeq: false */
for ( ; cur != this; cur = cur.parentNode || this ) {
/* jshint eqeqeq: true */
// Don't check non-elements (#13208)
// Don't process clicks on disabled elements (#6911, #8165, #11382, #11764)
if ( cur.nodeType === 1 && ( cur.disabled !== true || event.type !== "click" ) ) {
You will you see a different handling of events according to the delegation type:
$(document).on("click", '#btn', function() {
console.log("world");
});
$(function () {
$('#btnToggle').on('click', function(e) {
$('#btn').prop('disabled', !$('#btn').prop('disabled'));
});
$('#btnTestClick').on('click', function(e) {
$('#btn').click();
});
});
<script src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
<button id="btn">Click Me</button>
<button id="btnToggle">Enable/Disable button</button>
<button id="btnTestClick">Test Click</button>
Of course, if you attach the event like in:
$('#btn').on("click", function() {
alert("world");
});
The behaviour is different and seems strange.

Using .prop() is the right way to do it. I think the issue is in the way that you are "testing" it. See this example where the buttons are disabled/enabled correctly using the toggle button regardless of whether the handler is attached via onclick or with jquery.
window.testFunc = function(event) {
if (!$('#myButton2').prop('disabled')) {
alert("hello");
console.log("hello");
}
}
$(document).ready(function() {
var button = $("#myButton2");
button.on("click", function(event) {
if (!$(this).prop('disabled')) {
alert("world");
console.log("world");
}
});
$('#toggleButton').click(function() {
$('#myButton1').prop('disabled', !$('#myButton1').prop('disabled'));
$('#myButton2').prop('disabled', !$('#myButton2').prop('disabled'));
});
$('#tester').click(function() {
$('#myButton1').click();
$('#myButton2').click();
});
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="button" id="myButton1" value="vanilla button (hello)" onclick="window.testFunc(event)"/>
<input type="button" id="myButton2" value="jquery button (world)"/>
<input type="button" id="toggleButton" value="toggle disabled"/>
<input type="button" id="tester" value="test the buttons"/>
The other obvious solution is to just use vanilla javascript. Just because you are using jQuery doesn't mean that everything "must" be done using it. There are some things that are fine to do without jQuery.
EDIT: I edited the snippet showing how you could prevent jquery's .click() from actually triggering the alerts.

You're calling the click function directly 3 times ( button.click() ) which fires regardless of disabled attribute.
The disabled property only responds to click events.
See the updated example:
var button = $("#myButton");
var button2 = $("#myButton2");
button.prop("disabled", false);
button.on("click", function() {
alert("world");
button2.prop("disabled", false);
});
button2.prop("disabled", true);
button2.on("click", function() {
alert("world");
button.prop("disabled", true);
});
<script src="https://code.jquery.com/jquery-1.12.2.min.js"></script>
<input type="button" id="myButton" value="button" onClick="alert('Hello')"/>
<input type="button" id="myButton2" value="button2" />

Function activate after two onclicks

Hey I'm using javascript+html only.
Is there any way to activate a function after the button has been clicked two (or more) times? I want the button to do NOTHING at the first click.

For a "doubleclick", when the user quickly presses the mouse button twice (such as opening a program on the desktop), you can use the event listener dblclick in place of the click event.
https://developer.mozilla.org/en-US/docs/Web/Reference/Events/dblclick
For a quick example, have a look at the below code. http://jsfiddle.net/jzQa9/
This code just creates an event listener for the HTMLElement of "item", which is found by using getElementById.
<div id="item" style="width:15px;height:15px;background-color:black;"></div>
<script>
var item = document.getElementById('item');
item.addEventListener('dblclick',function(e) {
var target = e.target || e.srcElement;
target.style.backgroundColor = 'red';
},false);
</script>
As for wanting the user to click an element X times for it to finally perform an action, you can do the following. http://jsfiddle.net/5xbPG/
This below code works by adding a click tracker to the HTMLElement and incrementing the click count every time it's clicked. I opted to save the clicks to the HTMLElement instead of a variable, but either way is fine.
<div id="item" style="width:15px;height:15px;background-color:black;"></div>
<script>
var item = document.getElementById('item');
item.addEventListener('click',function(e) {
var target = e.target || e.srcElement;
var clicks = 0;
if(target.clicks)
clicks = target.clicks;
else
target.clicks = 0;
if(clicks >= 4) {
target.style.backgroundColor = 'red';
}
target.clicks += 1;
},false);
</script>
== UPDATE ==
Since you recently posted a comment that you want two different buttons to be clicked for an action to happen, you would want to do something like this... http://jsfiddle.net/9GJez/
The way this code works is by setting two variables (or more) to track if an element has been clicked. We change these variables when that item has been clicked. For each event listener at the end of changing the boolean values of the click state, we run the function checkClick which will make sure all buttons were clicked. If they were clicked, we then run our code. This code could be cleaned up and made to be more portable and expandable, but this should hopefully get you started.
<input type="button" id="button1">
<input type="button" id="button2">
<div id="result" style="width:15px;height:15px;background-color:black;"></div>
<script>
var result = document.getElementById('result');
var button1 = document.getElementById('button1');
var button2 = document.getElementById('button2');
var button1Clicked = false;
var button2Clicked = false;
button1.addEventListener('click',function(e) {
button1Clicked = true;
checkClick();
},false);
button2.addEventListener('click',function(e) {
button2Clicked = true;
checkClick();
},false);
function checkClick() {
if(button1Clicked && button2Clicked) {
result.style.backgroundColor = 'red';
}
}
</script>

Two ways you can do this, one would be to have a data attribute within the html button that identifies whether the click has been done.
<button id="btn">Click Me!</button>
<script>
var clickedAlready = false;
document.getElementById('btn').onclick = function() {
if (clickedAlready) {
//do something...
}
else
clickedAlready = true;
}
</script>
While global variables aren't the best way to handle it, this gives you an idea. Another option would be to store the value in a hidden input, and modify that value to identify if it's the first click or not.

Maybe something like this?
var numberTimesClicked = 0;
function clickHandler() {
if (numberTimesClicked > 0) {
// do something...
}
numberTimesClicked++;
}
document.getElementById("myBtn").addEventListener("click", clickHandler);

Set focus on a div in a javascript function

So I have a javascript function that displays the div that I am hiding, I am wondering how I then setfocus on the div so it goes down right to it on the page. I say setfocus because I have tried it earlier but it didnt work. Here is the function and the idea of focusing that i have.
<script>
function toggle_travelarea(id) {
var e = document.getElementById(id);
document.getElementById("canada").style.display = 'none';
document.getElementById("asia").style.display = 'none';
document.getElementById("australia").style.display = 'none';
document.getElementById("newzealand").style.display = 'none';
document.getElementById("africa").style.display = 'none';
document.getElementById("usa").style.display = 'none';
document.getElementById("samerica").style.display = 'none';
document.getElementById("europe").style.display = 'none';
e.style.display = 'block';
document.getElementByClassName('slidedeck').focus()
}
</script>
area i want to set focus to!
<div class="slidedeck">

Actually thought this didnt work but used an href to the anchor div id and then an onclick for the function and it worked properly. Thanks for the input everyone

I'm afraid you have to do a bit with math and use scrollTo.
Here's example -> http://jsbin.com/epozur/4
Basically:
HTML
<div id="hidden">
</div>
<button id="show">show</button>
JS
var btn = document.getElementById('show'),
hidden = document.getElementById('hidden');
btn.addEventListener('click', function () {
hidden.style.display = 'block';
scrollTo(0, hidden.offsetTop);
});
That should give you idea how to go further.
mz

How to read input from text on button click unobtrusively in Javascript?

How to read input from text on button click unobtrusively in Javascript? Can anyone provide a sample?
<script type="text/javascript>
window.onload = function() {
var btn = document.getElementById(
"btn"
);
btn.addEventListener("click",function() { alert("bar"); },false);
}
</script>
and in the body:
<div id="content">
<input type="text" id="percent" value="" />
<button id="btn">click</button></div>

Yes, addEventListener (with IE's attachEvent) is the most unobtrusive. To get the value of the textbox you simply use the .value property of the textbox.
<script type="text/javascript">
window.onload = function () {
var btn = document.getElementById("btn");
if (btn.addEventListener) {
btn.addEventListener("click", btnClick, false);
} else if (btn.attachEvent) {
btn.attachEvent("onclick", btnClick);
}
};
function btnClick() {
alert(document.getElementById("percent").value);
}
</script>