Develop Reference

JS: Change select option value on being selected with prompt?

I've looked around and I don't see this being asked before.
I have a select box, like so:
<select onchange="change()">
<option value="" selected>Option 1</option>
<option value="30">Option 2</option>
<option value="90">Option 3</option>
</select>
I want to add another option...
<option value="custom">Option 4</option>
...that when chosen (clicked) an alert box will popup asking the user to type in a number (in the case 30 or 90 weren't viable options, as in the values of the option's) to replace the value of the option.
<script>
function change() {
if(value == "custom") {
value = prompt("Please enter a new number:", "60");
}
}
</script>
I wanted to know what the best way to do this is with plain old javascript - I'll use jQuery if I have to.
Any ideas? An example would be great as well.

Take a look at this code. I think this is what you're trying to do:
HTML
<select id="optionvals" onclick="change()">
<option value="" selected>Option 1</option>
<option value="30">Option 2</option>
<option value="90">Option 3</option>
<option value="custom">Option 4</option>
</select>
JS
function change() {
var oItem = document.getElementById('optionvals');
var value = oItem.options[oItem.selectedIndex].value;
if(value == "custom") {
alert("you've clicked b");
value = prompt("Please enter a new number:", "60");
oItem.options[oItem.selectedIndex].value = value;
console.log(oItem.options[oItem.selectedIndex].value)
}
}
What this does is prompt you on the change only if the selected value in the options is custom. Then after you choose a custom value, it will rewrite the value of that the custom option element to the value you just entered in the prompt. I logged the new value after assigning it to show you that it is working.
Here is a fiddle: https://jsfiddle.net/ng7xvy05/

Your onchange event is the appropriate way to handle this. This is mostly a matter of user interface (UX) design though. To do this in the prompt fashion you ought to use parseFloat:
change() {
var value = prompt('You\'ve chosen Other. Please enter a value', '60');
if(value) {
value = parseFloat(value);
// apply it to your model
} else {
// apply NULL to your model
}
}
From a UXD point of view I would use a typeahead input. It would autosearch known answers but also allow the user to input their own. This is not standard html so you would need to write this yourself or use jquery. But from a user interface design point of view, prompts suck.

Check how many selects have had an options selected using jQuery

I got a bunch of selects:
<select name="paraquien" class="selectpicker form-control paraquien" id="paraquien" onchange="mostrarPreguntas();">
<option value=""><?=__('¿Para quién es el plan?')?><span class="glyphicon glyphicon-triangle-bottom"></span></option>
<option value="1"><?=__('Para mi')?> <span class="glyphicon glyphicon-triangle-bottom"></span></option>
<option value="2"><?=__('Para regalar')?><span class="glyphicon glyphicon-triangle-bottom"></span></option>
</select>
and I would like to know if all of them have been selected, and in that case trigger an event. I've tried this far:
jQuery('.paraquien option:selected')
Getting this result array:
[
<option value=​"1">​Para mi ​</option>​,
<option value=​"1">​Hombre​</option>​,
<option value=​"3">​Estudiante​</option>​,
<option value>​Su situación sentimental​</option>​,
<option value>​¿Tiene hijos?​</option>
​]
You can see every option selected has a value attribute set, what I would like to know is how to get just the options which value has been already set, in the same selector mentioned before.
Any Idea?

You can use filter() to check for select elements where the value is still ''. Try this:
var $unchosenSelects = $('.paraquien').filter(function() {
return $(this).val() == '';
});
if ($unchosenSelects.length) {
// there was at least one select within nothing chosen...
}
Similarly you could use map() to get all the values in an array, then $.inArray to check for empty strings:
var chosenValues = $('.paraquien').map(function() {
return $(this).val();
});
if ($.inArray(chosenValues, '') != -1) {
// there was at least one select within nothing chosen...
}

Jquery event for option box and typing action

I am doing the jquery event programming for option box for premium box.
For example, i can type on the option box.
So, I type in the option box instead of selecting my select option box.
the following code is the example:
But seems like it is not correct. Is the event is 'change' event ?
My HTML code is as following:
<div id = 'divContent'>
<select id="my_id" style="width: 120px;"
onchange="$('input#my_id').val($(this).find('option:selected').text());"
name="my_id">
<option value="10000">10000</option>
<option value="20000">20000</option>
<option value="30000">30000</option>
<option value="50000">50000</option>
<option value="80000">80000</option>
<option value="100000">100000</option>
</select>
</div>

You need to replace my_id with the id of your select box:
$("#divContent").on('change', "select[id='my_id']", function () {
Will work only when you have a select like:
<select id="my_id">
...

I don't see any elements with the id divContent so change the first line to
$("select[id='my_id']").on('change', function () {
Secondly, even when the code is working, with the example given, there won't be any alerts because none of the if statements will evaluate to true

You have a syntax error here -
if (selectedValue = '') {
alert("Please enter Premium")
}
it should be == not =
if (selectedValue == '') {
alert("Please enter Premium");
}
you can also use -
if(!selectedValue) or if(selectedValue == null)

jQuery validation on select box not working

I am using jQuery validation plugin for client side validation, but my validation does not work on my select box.
HTML
<select id="select" class="required">
<option value="-1">Choose</option>
<option value="child">test2</option>
</select>
JavaScript
$("#formid").validate({
select: {
required: function(element) {
if ($("#select").val() == '-1') {
return false;
} else {
return true;
}
}
}
});
How do I get this working?

A simple way to fix this problem is to give the non valid option the value of "". Then simply call validate on your form and it will not submit when "Choose" is selected.
HTML
<form id="formid">
<select name="select" class="required">
<option value="">Choose</option>
<option value="child">test2</option>
</select>
<input type="submit" />
</form>​
JavaScript
$("#formid").validate(); ​
Demo

Although this probably works with some of the aforementioned methods,if you're looking to use a custom validation function, you should use addMethod as documented here: http://docs.jquery.com/Plugins/Validation/Validator/addMethod
So you would first add the method through something like
$.validator.addMethod("requiredSelect", function(element) {
return ( $("#select").val() !='-1' );
}, "You must select an option.");
Then simply assign the validator with
$("#formid").validate({
rules: {
select: { requiredSelect : true }
}
});

For some reason no solution provided worked in my case, it boiled down to jQuery Validate calling the "optional" check on the value of the drop down, which that called the !required rule.
When the select box selected an empty value, the required showed "false" which inverted meant it was always optional when the required failed, so it never ran the required rule.
I overwrote the optional function with the below, which returned "False" on optional if it was a required item:
// Get Select to work
$.validator.prototype.optional = function (element) {
var val = this.elementValue(element);
// Custom logic to get Select to show validate when value is empty
if (element.nodeName.toLowerCase() === "select") {
if (element.hasAttribute("data-val-required") || element.hasAttribute("required")) {
return false;
}
}
return !$.validator.methods.required.call(this, val, element) && "dependency-mismatch";
};

instead of:
$("#select").val()
try:
$("#select :selected").val()
$("#select").val() returns all the option values instead of the selected one.
Here, my assumption is that you want to check if the user has chosen the option -1 when the control report-crime is validated.

by default
<option value="">Choose</option>
works with
required: true

There is missing name attribute in your select element.
In my case that was the issue since the jQuery Validatation Plugin looks for the name not id while validating.

HTML/JS: Validating value in <selected>-list

I'm really new to this and working on a JavaScript code and I want to see if a dropdownlist has any choosen value. How do i do that?
I tried:
var selectObj = form.document.getElementById('myListId');
var selectInd = selectObj.selectedInd;
and tried:
if(selectInd == "")
to check if it was empty.
What do I need to change to make it work?
Thanks in advance!

A drop-down, by design, always has a value selected. If you just want to leave an empty value first to not choose something for the user, you can simply check if it's value is empty.
document.getElementById("validate").onclick = function() {
if (document.getElementById("foo").value == "")
alert("invalid");
else
alert("valid");
};
Live example
According to comments, this might not work in older versions of IE. Be sure to test it there if you need to support those browsers.

HTML
<select id="myListId">
<option value="">- Select an option-</option>
<option value="1">Option 1</option>
<option value="2">Option 2</option>
<option value="3">Option 3</option>
</select>
Javascript
function checkvalue(){
var selectObj = form.document.getElementById('myListId');
if (selectObj.value != "") {/* DO something */}
}
Now you can execute this function on change of the select box, or when you submit the form, it is up to you.

Try to read this example.
You are trying compare a number (selectObj.selectedIndex) with a string (""), you should write something like this:
var selectObj = document.getElementById('myListId'),
selectInd = selectObj.selectedIndex,
selectedVal = selectObj.options[selectInd].value;
if(selectedVal== "") {
/* do your stuff*/
}
Only to notice: This only would work (detect a value equal to "") with an html like this:
<select id="myListId">
<option value="" selected="selected">Empty value</option>
<option value="1">Non empty value</option>
</select>
Or when the user has been selected the option "Empty value".
EDIT:
Try with this demo. This demo also works in IE7.