Develop Reference

How to show a message when a button is clicked

I want to show the following message when the button below is clicked using jQuery
<p class="msg-confirm" id="msgConf">
Great! You got this. Let's continue.
</p>
Button:
<input type="button" value="Start" class="btn-start" id="exec">
This message is set as none in CSS:
.msg-confirm{
display: none;
}
I have this function that worked before on a similar context, but without the validation. If the checkbox below is checked, I want this function working.
$("#exec").click(function(){
if($('#d3').is(':checked')){
$("#msgConf").show('slow');
}
});
Checkbox:
<input type="radio" name="image" id="d3" class="input-step1 aheadF1"/>

Let's make use of the simplicity of some of the new features of jQuery such as the .prop() method that will allow us to verify if a checkbox or radio button is checked. For the purpose of this example, I switched the input to a checkbox since it is more appropriate UX/UI wise speaking, however, this property can be verified in both controls. We will use the toggleClass() method of jQuery to toggle the class that hides the P tag and its content initially. I certainly hope this helps.
Happy coding!
$(document).ready(function () {
$("#exec").click(function () {
if ($('#d3').prop('checked')) {
$("p").toggleClass("msg-confirm");
} else {
alert("Please select the checkbox to display info.");
}
});
});
.msg-confirm {
display: none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<p class="msg-confirm">
Great! You got this. Let's continue.
</p>
<input type="button" value="Start" class="btn-start" id="exec">
<input type="checkbox" name="image" id="d3" class="input-step1 aheadF1"/>

Try this
$("#exec").on("click",function (){
if($('#d3').is(':checked')){
$("#msgConf").css("display","")
}
})

Activate Checkbox when clicking on element

When I click on an element, it should (only) activate/tick a checkbox, but it doesn't work.
HTML:
<input type="checkbox" id="collapsible" name="collapsible" /> <br />
<p class="member">
Activate Checkbox
</p>
Javascript:
$(".member").on("click", function() {
$('input[id $=collapsible]').attr('checked', this.checked);
});
http://jsfiddle.net/et7uym09/

I changed your code a little bit, you got already the right base.
this.checked is not defined in this context, so you have manually set it to true.
$(".member").on("click", function() {
$('#collapsible').attr('checked', true);
});
also you can use $('#collapsible').attr('checked', true); instead of $('input[id $=collapsible]').attr('checked', true);
working jsfiddle here: http://jsfiddle.net/zsL15wog/5/
if you want to toggle the checked state of the checkbox do something like this:
$(".member").on("click", function() {
var isChecked = $('#collapsible').prop('checked');
$('#collapsible').attr('checked', !isChecked);
});
fiddle: http://jsfiddle.net/zsL15wog/4/
Hope i could clear the things a bit more up :)
If you got other problems with this code, let me know.

What about <label>? Nothing extra necessary (unless you want a little styling on your text).
<label for="collapsible" style="cursor: pointer;">
Activate Checkbox
<input type="checkbox" id="collapsible" name="collapsible" />
<label>

$(".member").on("click", function() {
$('#collapsible').attr('checked',true);
});
Please try the above code

Replacing checkboxes with images?

I am trying to replace three check boxes within an html form with three different images. The idea being that the user can select the pictures by clicking on them rather than clicking on a check box. I've been putting togther some code but can't figure out how to make all the checkboxes selectable. At the moment only the first images works when it is clicked on. Can anyone help me? I'm a real novice with javascript I'm afraid. See fiddle here
The form
<form id="form1" action="" method="GET" name="form1">
<div class="col-md-3">
<img src="https://cdn2.iconfinder.com/data/icons/windows-8-metro-style/128/unchecked_checkbox.png" title="blr" id="blr"><input type="checkbox" id="imgCheck" name="pic1" value=9></div><div class="col-md-3">
<img src="https://cdn2.iconfinder.com/data/icons/windows-8-metro-style/128/unchecked_checkbox.png" title="blr" id="blr"><input type="checkbox" id="imgCheck" name="pic2" value=12></div><div class="col-md-3">
<img src="https://cdn2.iconfinder.com/data/icons/windows-8-metro-style/128/unchecked_checkbox.png" title="blr" id="blr"><input type="checkbox" id="imgCheck" name="pic3" value=7></div>
<input type="submit" name="submit" value="Add" />
</div>
</form>
The javascript
$('#blr').on('click', function(){
var $$ = $(this)
if( !$$.is('.checked')){
$$.addClass('checked');
$('#imgCheck').prop('checked', true);
} else {
$$.removeClass('checked');
$('#imgCheck').prop('checked', false);
}
})

Why use JavaScript at all? You can do this with CSS, the :checked attribute and a label element.
input[type=checkbox] {
display: none;
}
:checked+img {
border: 2px solid red;
}
<label>
<input type="checkbox" name="checkbox" value="value">
<img src="http://lorempixel.com/50/50/" alt="Check me">
</label>

This is happening because you're using the same ID more than one. IDs should be unique. Instead of using id="blr", try using class="blr". I updated the fiddle:
http://jsfiddle.net/0rznu4ks/1/

First, as Amar said, id should be unique. Use classes for multiple elements.
Also pay attention for semicolons and closing html tags.
To your question:
use the function .siblings() to get the relevant checkbox element.
$('.blr').on('click', function () {
var $$ = $(this);
if (!$$.is('.checked')) {
$$.addClass('checked');
$$.siblings('input.imgCheck').prop('checked', true);
} else {
$$.removeClass('checked');
$$.siblings('input.imgCheck').prop('checked', false);
}
});
See demo here:
http://jsfiddle.net/yd5oq032/1/
Good luck!

Inside an id div find all the checkbox and check and hide other unchecked

i am trying to learn and create a jquery which $("#answer") and find all the checkbox inside and check. As an example if checkbox inside #a1 is checked other div (a2,a3,a4) is hidden or other message come out. if i uncheck the #a1 all the div will come out again.
Please enlighten me on the code.
<div id="answer">
<div id="a1">A.<input type="checkbox" name="a1" onclick="cbox()" ></input></div>
<div id="a2">B. <input type="checkbox" name="a2"onclick="cbox()"></input></div>
<div id="a3">C. <input type="checkbox" name="a3"onclick="cbox()"></input></div>
<div id="a4">D. <input type="checkbox" name="a4"onclick="cbox()"></input></div>
</div>
function cbox() {
if (this checkbox is checked) {
target other div inside (#answer) and add .hide()
}
}
2)Is there anyway to add a trigger where i don't need to use onlick="cbox" ?
tq

It's better to use .click() instead of inline javascript onclick.
However, you should use .change() event for input elements instead of click:
$('input[type="checkbox"]').change(function() {
$(this).parent().siblings('div').toggle(!this.checked);
});
Fiddle Demo

Use .change() event instead of .click(). Try this:
$('input[type="checkbox"]').change(function() {
$(this).parent('div').siblings('div').toggle(!this.checked);
});
DEMO

Try this:
$("#answer input").change(function () {
if ($(this).is(":checked")) {
$("#answer input").not(this).each(function () {
$(this).parent().css("display", "none");
})
} else {
$("#answer input").not(this).each(function () {
$(this).parent().css("display", "block");
})
}
});
DEMO

How to grey out checkbox unless radio button is selected?

very new to javascript, but any help to get me started would be appreciated. I have a simple form:
<div><input type="radio" name="o1" id="burger" />Burger</div>
<div id="yesFries"><input type="checkbox" name="e1" id="fries" />Fries with that?</div>
<div><input type="radio" name="o1" id="pizza" />Pizza</div>
<div><input type="radio" name="o1" id="hotdog" />Hot Dog</div>
I want the "Fries" checkbox greyed out unless the "Burger" radio button is selected. I'm not sure if Javascript or CSS is the best way to do it. Thanks in advance!

what you want to do is set the elements disabled, until the state of the radio changes, that'd be done with javascript, and then you'd add/remove the disabled class in the onchange of the radio button.
What javascript libraries are you considering using? jQuery would make this fairly simple.
$('#burger').change( function () {
if ($('#burger').checked() ) {
$('#fries').removeClass('disabled');
} else {
$('#fries').addClass('disabled');
}
});

Actually with a bit CSS3 you can mock up a very simplistic solution.
Here we don't gray the button out, but you make it visible just if the checkbox is checked.
But, we could also gray it out with a bit more of CSS on top of this example.
You will always have to consider what kind of support you want to offer.
But if you are fine with it working on modern browsers, just give it a go.
Here's the HTML
<label>
<input type="checkbox" name="test" />
<span>I accept terms and cons</span><br><br>
<button>Great!</button>
</label>
Here's the CSS
button { display: none}
:checked ~ button {
font-style: italic;
color: green;
display: inherit;
}
And here's the DEMO http://jsfiddle.net/DyjmM/

I've noticed that you don't specify whether or not you can use jQuery. If that's an option, please see one of the other posts as I highly recommend it.
If you cannot use jquery then try the following:
<script>
function setFries(){
var el = document.getElementById("burger");
if(el.checked)
document.getElementById("fries").disabled = false;
else
document.getElementById("fries").disabled = true;
}
</script>
<div><input type="radio" name="o1" id="burger" onchange="setFries();"/>Burger</div>
<div id="yesFries"><input type="checkbox" name="e1" id="fries" disabled="disabled"/>Fries with that?</div>
<div><input type="radio" name="o1" id="pizza" onchange="setFries();"/>Pizza</div>
<div><input type="radio" name="o1" id="hotdog" onchange="setFries();"/>Hot Dog</div>​
Simple example on jsFiddle

If you're using jQuery, a really-easy-to-use Javascript library (that I would highly recommend for beginners), you can do this in two steps by adding some code to a script tag in your page containing:
$(function(){
$("#burger").change(function() {
if ($(this).is(':checked')) $("#fries").removeAttr("disabled");
else $("#fries").attr("disabled", true);
});
});
This code does three things:
Listens for change events on #burger.
When a change occurs, execute the provided function.
In that function, set the disabled attribute of #fries to the checked property of #burger.

use JQuery
$().ready(function() {
var toggleAskForFries = function() {
if($('#burger').is(':checked')) {
$('#yesFries').show()
else
$('#yesFries').hide()
}
return false
}
toggleAskForFries()
$('#burger').change(toggleAskForFries)
}

Using jQuery: http://jsfiddle.net/kboucher/cMcP5/ (Also added labels to your labels)

You nay try this without any function library
<input type="checkbox" name="e1" id="fries" disabled />
JS
window.onload=function(){
var radios=document.getElementsByName('o1');
for(i=0;i<radios.length;i++) radios[i].onclick=checkFire;
};
function checkFire(e)
{
var fires=document.getElementById('fries');
var evt=e||window.event;
var target=evt.target||evt.srcElement;
if(target.checked && target.id==='burger') fires.disabled=false;
else
{
fires.checked=false;
fires.disabled=true;
}
}
DEMO.