I'm beginner in javascript. I got an assignment to know about onchange keyword in javascript. i had seen this function is using different controls. I was unable where exactly to use this function.
what is onchange() in javascript? and for which controls we will use ? why will use in onchange() ?
please Explain in briefly with example?
The onchange property is fired when the element loses the focus or the content of the element have changed since the last time. It works <input>, <select>, and <textarea> elements
Here is an example of onchange applied on input type='text'
JS
function showContent(elem) {
var value = elem.value;
alert(value)
}
HTML
<input type="text" onchange="showContent(this)">
Here the onchange event eill fire as soon as tab or focus out of the element
You can use onchange with other input type like radio,checkbox,file
DEMO
Related
I am having an issue trying to trigger the test() function when updating the input of type text "testName" using the DOM. Does it have something to do with the DOM itself? It works when I am directly clicking on the input of type text and modify it, but not when another JS function access it through DOM to modify it.
document.getElementById('testID').value = "test";
Thank you
If you need to trigger the onchange event your code has to be like shown below
document.getElementById('testID').value = "test";
document.getElementById('testID').onchange();
Hope this solves your problem.
unlike a text field, a text area has no value that gets populated. make a div with id="testID" inside the text area and use that instead.
document.getElementById("testID").innerHTML="New text!";
if it is a text field, then your code should owrk
document.getElementById('testID').value = "something";
what are you using to trigger the event? onclick? onchange? what's it related to
I'm using labels for my form, like this :
<label for="foo" id="bar">Label</label>
<input type="checkbox" id="foo" />
I want to hide an element when the user uncheck the box, and show it otherwise.
The problem is, if I bind the click event to "foo", it'll only works when the user clicks on the checkbox itself and not on the label. Therefore, do I also need to bind a click event on the label ? Or should I enclose both elements within a span ?
My HTML already contains 2344 elements, so I'd like to do it without adding anything, and without doubling the JavaScript code or the selector, if possible.
Instead of binding with the click() event, you should bind using the change() event, then however this change is triggered the outcome will be the same:
$('#foo').change(
function(){
// do whatever
});
References:
change().
The change event should fire for the input whether the label or input is clicked:
$("#foo").change(function () { ... });
Example http://jsfiddle.net/andrewwhitaker/6LMXW/
I have a calendar which comprise of an input tag and an image on click of image calendar popups comes and sets the value for input tag using javascript.
now i have added onchange event on input tag which doesnt gets triggered since m changing the value using javascript, so what should be done to trigger it i dont want to trigger it explcitly
i tried focusing on input on click of image and focus out on setting the data(into input element) but it didnt worked any workaround?
You can call the onchange handler manually.
Example: http://jsfiddle.net/NQCy7/
element.value = 'new value';
element.onchange();
just tested what you described, it's the same problem here.
a simple workaround would be to call the onchange-method directly (where you're doing the .focus()/.blur() now)
On this page:
http://www.blackdownluxurylettings.co.uk/place_booking/2010-3-18,2
I am using an onchange event on the "number of days" select box to update the "departure date" field.
But currently nothing is happening.
Any ideas?
Just looking at it quickly: wouldn't you want the ONCHANGE event attached to the SELECT tag rather than the individual options?
You can bind it this way using JQuery:
$("#ddlNumberOfDays").bind('change', mainPharmacy_Change)
Maybe for javascript, you should just try 'change'.
If I recall correctly, the regular Javascript onChange event only fires once the select box loses focus AND it's contents have been changed. I don't know how jQuery achieves it, but their change method will fire whenever the contents are updated.
Also, I get the following error in my Javascript console when loading your page:
[cycle] terminating; zero elements found by selector
HI,
In JavaScript when value is set to a hidden input control, which event is fired?
Whenever you change the value of a hidden field using script, it wont fire any event. But you can manually trigger the event if you are using jQuery.
Lets assume that you have the following hidden field
<input type="hidden" id="hid" value="0"
onchange="alert('Caught the hidden event');" />
When you change the value of the field using following code, it will not display the alert message.
$("#hid").val("2");
But you can trigger the change event using the following code
$("#hid").val("2").change();
Above code will display the alert message.
A value (aside from the initial value) can only be set on a hidden input by using scripting, and events do not generally fire in response to scripts.
It might trigger a Mutation event, but browser support for them is not all that widespread yet.
In general, if you want to do something when you script changes the value of a hidden input — make the script do the other thing at the same time.
I'm guessing that 'onchange' would fire.