Onchange event for multiple dropdowns issue - javascript

I have a list like this:
<form>
<select id="List_22" >
<option value="default">Default</option>
<option value="1">Oil</option>
<option value="2">Gas</option>
<option value="3">Power</option>
</select>
<form>
I want to launch a function upon dropdown change, so this works fine:
document.getElementById("List_22").onchange = function() {...
I however have multiple dropdowns that should all use the same function. I have tried to use the below wildcard but it does not work
document.getElementById("[id^=L]").onchange = function() {
What am I doing wrong? I am going slightly barmy. Thank you all for your time.

The issue is document.getElementById looks for an exact ID match for a single element, so it doesn't support attribute selectors and nor does it return multiple elements.
In plain old JavaScript you can use document.querySelectorAll which supports CSS selectors, and the attribute selector. Note that this isn't supported before IE8.
var list = document.querySelectorAll('[id^=L]');
for(var i=0; i<list.length; i++){
list[i].onchange = function(){
// do something on change....
};
}
Or since you have jQuery tagged, a jQuery version:
$('[id^=L]').change(function(){
// do something on change....
});
Side note: In both cases, I would prefer to make the attribute selector more specific such as select[id^=List_].

$('form select').on('change', function(){
// Your code here
});

In plain javascript, you could do this generic search which should work in every browser and no need to regular expressions.
var dropdowns = document.getElementsByTagName("select"),
item;
for (var i = 0, count = dropdowns.length; i < count; i++) {
item = dropdowns[i];
if (item.id && item.id.indexOf("List_") == 0) {
item.onchange = function () {
alert(this.options[this.selectedIndex].text);
};
}
}
Working example: http://jsfiddle.net/Rq9nb/

Best procedure for cases like this would be, to add a common class to all the dropdowns for which you want to call the function on change. For ex: add 'trigger-change' class for all your required dropdowns. Then below bind event should work perfect for you.
$('form select.trigger-change').on('change', function(){
// Your code here
});
This way, you can choose the dropdowns for which you want to trigger a change event funciton and you can also have dropdowns which are not triggering the change event functions.
Hope this helps :)

Related

Unable to select first item of dynamically generated select with jquery

I am dynamically generating a select contol with jQuery on my page. The generated select is given below.
<select id="autoCompleteSelect" size="5" class="autoSelect">
<option value="firstVal">firstVal</option>
<option value="secondVal">secondVal</option>
</select>
Now i want to select the first item of this select control on my textbox keyup event. But i cannot do so. The keyup code is -
$('#searchInput').keyup(function (e) {
var a = $(".autoSelect").val();
var myDDL = $('.autoSelect');
myDDL[0].selectedIndex = 0;
});
however when i do not generate select dynamically and just put it on the page from the beginning. Everything works fine. What could be the solution for dynamically generated select.
$("#autoCompleteSelect").val($("#autoCompleteSelect option:first").val());
http://jsfiddle.net/oob1ybxp/
If working with dynamically generated content, it is best to use event delegation concept like below:
// document here can be replaced with closest parent which
// created/ existed without dynamic load
// provided context parameter to on function
$(document).on('keyup','#searchInput', function (e) {
var a = $(".autoSelect").val();
var myDDL = $('.autoSelect');
myDDL[0].selectedIndex = 0;
});
Read this .on() also.
Keep your code in the form something like
$('someStaticSelector').on('keyup', 'DynamicAddedSelector', function (e) {
var a = $(".autoSelect").val();
var myDDL = $('.autoSelect');
myDDL[0].selectedIndex = 0;
});

How to select the DropDownList/Select that triggered the change event

I'm new to JQuery and I noticed this line $('#DivID [type=checkbox]') and I was wondering if I can also find the select or option tags using the same method.
Update: I have a div that has more than more tag, I'm trying to get the DropDownList/Select that it's value's just changed.
Update2 I'm using InstaFilta a JQuery plugin that filter the content based on a customized attribute appended to my content tags. Below is a snippet for the function that do the same when working with CheckBoxes, and I'm trying to edit it to work with DropDownLists/Select controls.
var $ex10Checkboxes = $('#ex10 [type=checkbox]');
$ex10Checkboxes.on('change', function() {
var checkedCategories = [];
$ex10Checkboxes.each(function() {
if ($(this).prop('checked')) {
checkedCategories.push($(this).val());
}
});
ex10.filterCategory(checkedCategories, true);
});
You would find the option tags as follows:
$("#DivID option")
Likewise the select tags:
$("#DivID select")
You can then iterate over the returned objects to inspect the individual elements:
var foo = $("#DivID option");
var i;
for (i = 0; i < foo.length; i += 1) {
console.log(foo[i].val()); //or whatever
}
To find the selected element you could check out this question:
$("#DivID option:selected")
I would suggest checking out the JQuery page on Selectors JQuery Selectors

How to select an option via jquery

I have a select form that looks kind of like this:
<select multiple="multiple" id="id_color_id" name="color_id"">
<option value="1">Red</option>
<option value="2">Blue</option>
<option value="3">Brown</option>
</select>
What I want to do is select the item above via javascript. This is actually part of a hidden form, so all I'm trying to do is leverage the serialize part of the form. I'm thinking it will just be easier to hack that after the serialize then to add this as well, but I also want to deselect any options that have already been selected.
So two questions:
How to select an option via javascript. All I will know is "Red", "Blue" or "Brown". I also have a look up dictionary that can get me the values as well.
How to deselect all options previous to selecting one of the above.
This is related to: Selecting options in a select via JQuery
Native Javascript:
var textToFind = 'Red';
var dd = document.getElementById('id_color_id');
for (var i = 0; i < dd.options.length; i++) {
if (dd.options[i].text === textToFind) {
dd.selectedIndex = i;
break;
}
}
or with jQuery:
$('#id_color_id option:contains('Blue')').prop('selected',true);
with variable:
var blue = "Blue";
$('#id_color_id option:contains(' + blue + ')').prop('selected',true);
And to deselect all selected options:
Native Javascript:
var elements = document.getElementById("id_color_id").options;
for(var i = 0; i < elements.length; i++){
if(elements[i].selected)
elements[i].selected = false;
}
jQuery:
$("#id_color_id option:selected").removeAttr("selected");
To select an option by it's content (considering what you posted is what you have)
$("#id_color_id option:contains('Red')").prop('selected',true);
jsFiddle Demo
You can set the value on the select box using the .val() method. Running this will reset any previously selected values, so you don't need to do anything specific to accomplish that part. You can also use an array to select multiple values, which may be of interest, since you are using a multi select.
$("#id_color_id").val(['1','2']);

Script to enable/disable input elements?

I'm wondering if it's possible for a script to enable/disable all input elements on the page with some sort of toggle button.
I googled it but didn't find anything too useful except for this:
http://www.codetoad.com/javascript/enable_disable_form_element.asp
but I'm not sure how to edit it for the toggle.
Something like this would work:
var inputs=document.getElementsByTagName('input');
for(i=0;i<inputs.length;i++){
inputs[i].disabled=true;
}
A working example:
$().ready(function() {
$('#clicker').click(function() {
$('input').each(function() {
if ($(this).attr('disabled')) {
$(this).removeAttr('disabled');
}
else {
$(this).attr({
'disabled': 'disabled'
});
}
});
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script>
<input type='text'></input>
<input type='text'></input>
<input type='text'></input>
<div id='clicker' style='background-color:#FF0000; height:40px; width:100px;'></div>
Here is a function to toggle all inputs on the page:
function toggle_inputs() {
var inputs = document.getElementsByTagName('input');
for (var i = inputs.length, n = 0; n < i; n++) {
inputs[n].disabled = !inputs[n].disabled;
}
}
It works by using the logical NOT operator (the exclamation point), which returns the opposite of the operand. For example, !true will return false. So by using !inputs[n].disabled, it will return the opposite of what it's currently set to, thereby toggling it.
If you need code to bind the click event to the button:
document.getElementById('your_button_id').onclick = toggle_inputs;
You can also use addEventListener, but see the linked page for more information, including compatibility with Internet Explorer. The code I gave above should work across all browsers with no trouble.
for (var i = 0; i < document.getElementyByTagName('input').length; i++) {
document.getElementsByTagName('input')[i].disabled = 'disabled';
}
http://code.google.com/p/getelementsbyclassname/
^^Robert Nyman has a "get elements by class" script. Basically you'd just assign all those input elements to the same class, and then do something like:
//Collapse all the nodes
function collapseNodesByClass(theClass){
var nodes = getElementsByClassName(theClass);
for(i = 0; i < nodes.length; i++){
nodes[i].style.display='none';
}
}
This is a piece of code I'm actually currently using to collapse everything with a given class name (it uses the script I mentioned above). But in any case I think the key to your problem is being able to refer to multiple elements at once, which that script will help you with.
Also the link in your question didn't work for me :(.

How do I access the "displayed" text of a select box option from the DOM?

Given the following HTML:
<select name="my_dropdown" id="my_dropdown">
<option value="1">displayed text 1</option>
</select>
How do I grab the string "displayed text 1" using Javascript/the DOM?
var sel = document.getElementById("my_dropdown");
//get the selected option
var selectedText = sel.options[sel.selectedIndex].text;
//or get the first option
var optionText = sel.options[0].text;
//or get the option with value="1"
for(var i=0; i<sel.options.length; i++){
if(sel.options[i].value == "1"){
var valueIsOneText = sel.options[i].text;
}
}
var mySelect = document.forms["my_form"].my_dropdown;
// or if you select has a id
var mySelect = document.getElementById("my_dropdown");
var text = mySelect.options[mySelect.selectedIndex].text;
Assuming you want the selected option's text:
var select = document.getElementById('my_dropdown');
for(var i = 0; i < select.options.length; i++) {
if(select.options[i].selected) {
break;
}
}
var selectText = select.options[i].text;
In Prototype:
var selectText = $$('#my_dropdown option[selected]')[0].text;
Edit: And jQuery for completeness' sake (assuming jQuery's CSS selector support is roughly equivalent to that of Prototype's):
var selectText = $('#my_dropdown option[selected]').get(0).text;
The displayed text is a child node of the option node. You can use:
myOptionNode.childNodes[0];
to access it, assuming the text node is the only thing inside the option (and not other tags).
EDIT: Oh yeah, as others mentioned, I completely forgot about:
myOptionNode.text;
Assuming you modified your code a bit to have an id / class on the and were using jQuery you could have something like the following. It will pop up an alert for each option with the text of the option. You probably won't want to alert for all the text, but it illustrates how to get at the text in the first place:
$('select#id option').each(function() {
alert($(this).text());
});
If you use a class instead of an id, then you'd just have to change the 'select#id' to 'select.class'. If you didn't want to add a class/id there are other ways to get at the select.
I leave figuring those ways out if you want to go that route as an activity for the reader.
If you were using Prototype, you could get at it like this:
$$('#my_dropdown option[value=1]').each( function(elem){
alert(elem.text);
});
The above is using a CSS selector that says find all option tags with value="1" that are inside the element that has id="my_dropdown".

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