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jQuery handler to know when at least 1 character has been typed into an input text element

I have a simple input like the following:
<input type="text" id="foo">
I tried using change() in order to detect when at least 1 character has been keyed in. The problem is, the event doesn't fire off until the input text box has lost focus.
Is there another event I can bind to and be able to trigger some code when at least 1 character has been typed?

You can use jQuery's keydown(). You can also try keypress(), which fires when the key is down, or keyup(), which is when the key is lifted up.
These all fire after a single key, not upon losing focus.
Therefore, you can try:
$("#test").keydown(function() {
$("#console").prepend(
(($(this).val().length) ?
"Not Empty" :
"Empty")
+ "<br />"
);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="test" />
<div id="console"></div>

You might give input a try.
$('#foo').on('input', function(){
if (this.value.trim().length) {
console.log('we got a char');
}
});
Input is filtered to be thing that change the actual input of the element. So you don't have to worry about random keys like function keys and stuff, enter press, etc.

Show Input Box on Check

You can see in the paper form attached what I need to convert into a web form. I want it to show the check boxes and disable the input fields unless the user checks the box next to it. I've seen ways of doing this with one or two elements, but I want to do it with about 20-30 check/input pairs, and don't want to repeat the same code that many times. I'm just not experienced enough to figure this out on my own. Anyone know anywhere that explains how to do this? Thanks!
P.S. Eventually this data is all going to be sent through an email with PHP.

I don't think this is a good idea at all.
Think of the users. First they have to click to enter a value. So they always need to change their hand from mouse to keyboard. This is not very usable.
Why not just give the text-fields? When sending with email you could just leave out the empty values.

in your HTML :
//this will be the structure of each checkbox and input element.
<input type="checkbox" value="Public Relations" name="skills" /><input type="text" class="hidden"/> Public Relations <br/>
in your CSS:
.hidden{
display:none;
}
.shown{
display:block;
}
in your jQuery:
$('input[type=checkbox]').on('click', function () {
// our variable is defined as, "this.checked" - our value to test, first param "shown" returns if true, second param "hidden" returns if false
var inputDisplay = this.checked ? 'shown' : 'hidden';
//from here, we just need to find our next input in the DOM.
// it will always be the next element based on our HTML structure
//change the 'display' by using our inputDisplay variable as defined above
$(this).next('input').attr('class', inputDisplay );
});
Have fun.

Since your stated goal is to reduce typing repetitive code, the real answer to this thread is to get an IDE and the zen-coding plug in:
http://coding.smashingmagazine.com/2009/11/21/zen-coding-a-new-way-to-write-html-code/
http://vimeo.com/7405114

Disabling form password autocompletion but not other fields

I know you can disable the autocomplete on a form by setting autocomplete="off" on the form itself.
The problem I have is, I want to prevent the browser from populating the password field but do not want to disable username or other fields.
The other thing to consider is legacy data. Using autocomplete="off" on the form (or even the field itself) does not prevent existing users with saved passwords from getting a free-pass. Or ones that use web inspector, change the value of autocomplete and submit, allowing themselves to save the password.
I know it is possible to change the password field name attribute to a random/new one on every visit. Regretfully, I am working with a java/spring back-end and I am being told this is NOT easily manageable without a huge refactor/override.
How would you architect this? How would you enforce that the field always starts empty? There is no consistent way for browsers to event notify you of pre-population by a password manager - some may fire an onChange, others may not.
I guess I can move fields around with javascript and build the real form on the fly and submit it but once again, this will have implications with spring security and validations etc. Any other ideas?

you can made a temp variable when onFocus is call to set a variable to true ( like userFocus )
and on the onChange attribut but a short code for reseting "value" to NULL if userFocus== false) kind of overkilling imo but migth work
EDIT
function reset()
{
if (document.getElementById("hidden").value!=" ")
{
document.getElementById("demo").value=" ";
}
else;
}
function getfocus()
{
document.getElementById("hidden").value=" ";
}
else;
}
<input type="password" id="pwd" onchange="reset()" onfocus="getfocus()"/>
<input type="hidden" id="hidden" value="not focus"/>

I had to find this solution for IE 11 (since it ignores the autocomplete attribute). It works fine in other browsers. Really more of a work around, but it works.
https://stackoverflow.com/a/20809203/1248536

I was recently faced with this problem, and with no simple solution since my fields can be prepopulated, I wanted to share an elegant hack I came up with by setting password type in the ready event.
Don't declare your input field as type password when creating it, but add a ready event listener to add it for you:
function createSecretTextInput(name,parent){
var createInput = document.createElement("input");
createInput.setAttribute('name', name);
createInput.setAttribute('class', 'secretText');
createInput.setAttribute('id', name+'SecretText');
createInput.setAttribute('value', 'test1234');
if(parent==null)
document.body.appendChild(createInput);
else
document.getElementById(parent).appendChild(createInput);
$(function(){
document.getElementById(name+'SecretText').setAttribute('type', 'password');
});
};
createSecretTextInput('name', null);
http://jsfiddle.net/N9F4L/

html <input type="text" /> onchange event not working

I am trying to do some experiment. What I want to happen is that everytime the user types in something in the textbox, it will be displayed in a dialog box. I used the onchange event property to make it happen but it doesn't work. I still need to press the submit button to make it work. I read about AJAX and I am thinking to learn about this. Do I still need AJAX to make it work or is simple JavaScript enough? Please help.
index.php
<script type="text/javascript" src="javascript.js"> </script>
<form action="index.php" method="get">
Integer 1: <input type="text" id="num1" name="num1" onchange="checkInput('num1');" /> <br />
Integer 2: <input type="text" id="num2" name="num2" onchange="checkInput('num2');" /> <br />
<input type="submit" value="Compute" />
</form>
javascript.js
function checkInput(textbox) {
var textInput = document.getElementById(textbox).value;
alert(textInput);
}

onchange is only triggered when the control is blurred. Try onkeypress instead.

Use .on('input'... to monitor every change to an input (paste, keyup, etc) from jQuery 1.7 and above.
For static and dynamic inputs:
$(document).on('input', '.my-class', function(){
alert('Input changed');
});
For static inputs only:
$('.my-class').on('input', function(){
alert('Input changed');
});
JSFiddle with static/dynamic example: https://jsfiddle.net/op0zqrgy/7/

HTML5 defines an oninput event to catch all direct changes. it works for me.

Checking for keystrokes is only a partial solution, because it's possible to change the contents of an input field using mouse clicks. If you right-click into a text field you'll have cut and paste options that you can use to change the value without making a keystroke. Likewise, if autocomplete is enabled then you can left-click into a field and get a dropdown of previously entered text, and you can select from among your choices using a mouse click. Keystroke trapping will not detect either of these types of changes.
Sadly, there is no "onchange" event that reports changes immediately, at least as far as I know. But there is a solution that works for all cases: set up a timing event using setInterval().
Let's say that your input field has an id and name of "city":
<input type="text" name="city" id="city" />
Have a global variable named "city":
var city = "";
Add this to your page initialization:
setInterval(lookForCityChange, 100);
Then define a lookForCityChange() function:
function lookForCityChange()
{
var newCity = document.getElementById("city").value;
if (newCity != city) {
city = newCity;
doSomething(city); // do whatever you need to do
}
}
In this example, the value of "city" is checked every 100 milliseconds, which you can adjust according to your needs. If you like, use an anonymous function instead of defining lookForCityChange(). Be aware that your code or even the browser might provide an initial value for the input field so you might be notified of a "change" before the user does anything; adjust your code as necessary.
If the idea of a timing event going off every tenth of a second seems ungainly, you can initiate the timer when the input field receives the focus and terminate it (with clearInterval()) upon a blur. I don't think it's possible to change the value of an input field without its receiving the focus, so turning the timer on and off in this fashion should be safe.

onchange only occurs when the change to the input element is committed by the user, most of the time this is when the element loses focus.
if you want your function to fire everytime the element value changes you should use the oninput event - this is better than the key up/down events as the value can be changed with the user's mouse ie pasted in, or auto-fill etc
Read more about the change event here
Read more about the input event here

use following events instead of "onchange"
- onkeyup(event)
- onkeydown(event)
- onkeypress(event)

Firstly, what 'doesn't work'? Do you not see the alert?
Also, Your code could be simplified to this
<input type="text" id="num1" name="num1" onkeydown="checkInput(this);" /> <br />
function checkInput(obj) {
alert(obj.value);
}

I encountered issues where Safari wasn't firing "onchange" events on a text input field. I used a jQuery 1.7.2 "change" event and it didn't work either. I ended up using ZURB's textchange event. It works with mouseevents and can fire without leaving the field:
http://www.zurb.com/playground/jquery-text-change-custom-event
$('.inputClassToBind').bind('textchange', function (event, previousText) {
alert($(this).attr('id'));
});

A couple of comments that IMO are important:
input elements not not emitting 'change' event until USER action ENTER or blur await IS the correct behavior.
The event you want to use is "input" ("oninput"). Here is well demonstrated the different between the two: https://javascript.info/events-change-input
The two events signal two different user gestures/moments ("input" event means user is writing or navigating a select list options, but still didn't confirm the change. "change" means user did changed the value (with an enter or blur our)
Listening for key events like many here recommended is a bad practice in this case. (like people modifying the default behavior of ENTER on inputs)...
jQuery has nothing to do with this. This is all in HTML standard.
If you have problems understanding WHY this is the correct behavior, perhaps is helpful, as experiment, use your text editor or browser without a mouse/pad, just a keyboard.
My two cents.

onkeyup worked for me. onkeypress doesn't trigger when pressing back space.

It is better to use onchange(event) with <select>.
With <input> you can use below event:
- onkeyup(event)
- onkeydown(event)
- onkeypress(event)

when we use onchange while you are typing in input field – there’s no event. But when you move the focus somewhere else, for instance, click on a button – there will be a change event
you can use oninput
The oninput event triggers every time after a value is modified by the user.Unlike keyboard events, it triggers on any value change, even those that does not involve keyboard actions: pasting with a mouse or using speech recognition to dictate the text.
<input type="text" id="input"> oninput: <span id="result"></span>
<script>
input.oninput = function() {
console.log(input.value);
};
</script>
If we want to handle every modification of an <input> then this event is the best choice.

I have been facing the same issue until I figured out how to do it. You can utilize a React hook, useEffect, to write a JS function that will trigger after React rendering.
useEffect(()=>{
document.title='fix onChange with onkeyup';
const box = document.getElementById('changeBox');
box.onkeyup = function () {
console.log(box.value);
}
},[]);
Note onchange is not fired when the value of an input is changed. It is only changed when the input’s value is changed and then the input is blurred. What you’ll need to do is capture the keypress event when fired in the given input and that's why we have used onkeyup menthod.
In the functional component where you have the <Input/> for the <form/>write this
<form onSubmit={handleLogin} method='POST'>
<input
aria-label= 'Enter Email Address'
type='text'
placeholder='Email Address'
className='text-sm text-gray-base w-full mr-3 py-5 px-4 h-2 border border-gray-primary rounded mb-2'
id='changeBox'
/>
</form>
Resulting Image :
Console Image

try onpropertychange.
it only works for IE.

Clear default values using onsubmit

I need to clear the default values from input fields using js, but all of my attempts so far have failed to target and clear the fields. I was hoping to use onSubmit to excute a function to clear all default values (if the user has not changed them) before the form is submitted.
<form method='get' class='custom_search widget custom_search_custom_fields__search' onSubmit='clearDefaults' action='http://www.example.com' >
<input name='cs-Price-2' id='cs-Price-2' class='short_form' value='Min. Price' />
<input name='cs-Price-3' id='cs-Price-3' class='short_form' value='Max Price' />
<input type='submit' name='search' class='formbutton' value=''/>
</form>
How would you accomplish this?

Read the ids+values of all your fields when the page first loads (using something like jquery to get all "textarea", "input" and "select" tags for example)
On submit, compare the now contained values to what you stored on loading the page
Replace the ones that have not changed with empty values
If it's still unclear, describe where you're getting stuck and I'll describe more in depth.
Edit: Adding some code, using jQuery. It's only for the textarea-tag and it doesn't respond to the actual events, but hopefully it explains the idea further:
// Keep default values here
var defaults = {};
// Run something like this on load
$('textarea').each(function(i, e) {
defaults[$(e).attr('id')] = $(e).text();
});
// Run something like this before submit
$('textarea').each(function(i, e){
if (defaults[$(e).attr('id')] === $(e).text())
$(e).text('');
})
Edit: Adding some more code for more detailed help. This should be somewhat complete code (with a quality disclaimer since I'm by no means a jQuery expert) and just requires to be included on your page. Nothing else has to be done, except giving all your input tags unique ids and type="text" (but they should have that anyway):
$(document).ready(function(){
// Default values will live here
var defaults = {};
// This reads and stores all text input defaults for later use
$('input[type=text]').each(function(){
defaults[$(this).attr('id')] = $(this).text();
});
// For each of your submit buttons,
// add an event handler for the submit event
// that finds all text inputs and clears the ones not changed
$('input[type=submit]').each(function(){
$(this).submit(function(){
$('input[type=text]').each(function(){
if (defaults[$(this).attr('id')] === $(this).text())
$(this).text('');
});
});
});
});
If this still doesn't make any sense, you should read some tutorials about jQuery and/or javascript.

Note: This is currently only supported in Google Chrome and Safari. I do not expect this to be a satisfactory answer to your problem, but I think it should be noted how this problem can be tackled in HTML 5.
HTML 5 introduced the placeholder attribute, which does not get submitted unless it was replaced:
<form>
<input name="q" placeholder="Search Bookmarks and History">
<input type="submit" value="Search">
</form>
Further reading:
DiveintoHTML5.ep.io: Live Example... And checking if the placeholder tag is supported
DiveintoHTML5.ep.io: Placeholder text

1) Instead of checking for changes on the client side you can check for the changes on the client side.
In the Page_Init function you will have values stored in the viewstate & the values in the text fields or whichever controls you are using.
You can compare the values and if they are not equal then set the Text to blank.
2) May I ask, what functionality are you trying to achieve ?

U can achieve it by using this in your submit function
function clearDefaults()
{
if(document.getElementById('cs-Price-2').value=="Min. Price")
{
document.getElementById('cs-Price-2').value='';
}
}