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Difference between form.submit() and having an input with type of "submit"

I have a HTML page containing a form. I want to make some fields "required". The problem is that I'm not using a <input type="submit"> in my form, instead, I use a Javascript function to submit the form because I need to send a Javascript variable to my server. Here is my code:
<form action="/toServer">
Username: <input type="text" name="usrname" required>
<input type="button" onclick="submitForm(this.form)" value="Submit">
</form>
var submitForm = function(frm){
var qstNbr = document.getElementById('hiddenField');
qstNbr.value = someJsVariable;
frm.submit();
}
So, Even is I have the required attribute in my input but the form is still being submitted even if I don't enter anything in the input.
Here is a JSFiddle of how I want my form to behave when clicking on the button without entering anything.
Anyone knows how form.submit() is different from having an <input> of type="submit" ?
EDIT: After following user2696779's answer and doing a little modification, here's the final working code:
<form action="/toServer">
Username: <input type="text" name="usrname" required>
<input type="submit" onclick="submitForm(this.form)" value="Submit">
</form>
var submitForm = function(frm){
if (frm.checkValidity()) {
var qstNbr = document.getElementById('hiddenField');
qstNbr.value = someJsVariable;
frm.submit();
}
}

Your current HTML input button isn't a submit type, it's a button type. The requred attribute on your input element is therefore ignored. To change this, change your button's type to submit:
<input type="submit" value="Submit">
Browsers which support the required attribute will now display a warning when the button is clicked:
JSFiddle demo.

Submitting using javascript will not trigger any validation. If you want to submit using a regular button + javascript and still have validation, you may use HTML5's checkValidity function to verify form fields, or the entire form.
For example, using JQuery:
if(!$('form')[0].checkValidity()) {
alert('not valid');
}
else {
$('form').submit();
}
See fiddle for working example: http://jsfiddle.net/8Kmck/2/

prefill text field using javascript

I have a simple javascript that I can't seem to get to work.
So what I'm trying to accomplish is a text field on my homepage that the user can type in(just 1 field). Submit it and it'll take them to another page with a text field that is pre filled with what they already typed in the first field.
<script type="text/javascript">
function go_page(page)
{
document.location.href = '/?page_id=11' + '#addressInput=' + addressInput;
}
</script>
When i fill in the 'addressInput' (for this example, lets say '90501')..
Currently, the url comes up as www.mywebsite.com/?addressInput=90501
Goal, i want it to be.. www.mywebsite.com/?page_id=11#addressInput=90501
This 'goal url' works when i type it in the address bar. I just need to figure out how to do that function automatically for the user..based on what they input in the first text field.
...any ideas?
EDIT 1
Here is the form code..
<form method="get" onsubmit=" go_page(this.page.value); return false">
<input type="text" name="addressInput" id="addressInput" size="30" />
<input type="submit" value="" class="submitButton" />
</form>
EDIT 2
just more info..
The user will be on the homepage and type in an 'address/zip code' in the text field and click submit.
Which will then take them to the locations page(page_id=11) that has a text field that's pre-populated with the 'address/zip' the user typed in on the homepage.

You could try grabbing the element in the form like this
<form method="get" onsubmit="go_page(this.addressInput); return false">
<input type="text" name="addressInput" id="addressInput" size="30" />
<input type="submit" value="" class="submitButton" />
</form>
And extracting the value of addressInput inside your function like this
function go_page(elem) {
var addressInput = elem.value;
window.location.href = "/?page_id=11#addressInput"+addressInput;
}
In Wordpress that should navigate you to the page id and add the hash to the end

Its not clear from the limited information provided, but have you stopped the default form submission behavior? Maybe the form if being submitted before your javascript is called. Capture the form submission and return:false or event.preventDefault() to stop it continuing with the submission.

If you want to have # in the URL, you have to encode it so instead of using # use %23. And do not forget that for separating values in URL you have to use &.
document.location.href = '/?page_id=11' + '%23addressInput=' + addressInput;
Update
Instead of document.location.href use window.location

Form fields value get reset without page load

Following is my code in which i am trying to accomplish, when user clicks on the submit button then my javascript function sets all the value to null in the textfields of the form whose id='contact_form' without loading the page . Kindly let me know how can i modify the following code to accomplish the functionality i've been trying to do.
Thanks!!
<script type='text/javascript'>
$(document).ready(function(){
$('#love').click(function(e) {
document.contact_form.name.value = '';
alert('aloha!!');
//stop the form from being submitted (not working fine)
e.preventDefault();
}
}
</script>
<form name='abc' action='' id='abc' >
<input type="submit" id='love' />
</form>
I have also tried the following function it worked fine but its not preventing from the page load
<script type='text/javascript'>
function js(){
document.contact_form.name.value = '';
//stop the form from being submitted (NOT WORKING!!)
preventDefault();
}
}
</script>

If you try onsubmit="return false;" in the form tag your form will not be submitted. Unfortunately it will NEVER be submit. Unless you are not planning to submit it via AJAX you have to modify your onsubmit event like this:
<form onsubmit="return callFunction()">
function callFunction() {
if(condition)
return true;
else
return false;
}

$("#abc").submit( function() {
// do everything you want.
return false; //will prevent the reload.
});

To have a function execute when the form submits you have to do something like this;
<form onsubmit="return validate();">
your form here
</form>
Then you can have your check in a function called 'validate()' (or whatever you want to call it)
Make sure the validate() function returns true is the form is allowed to submit, or returns false if the page is not allowed to submit.
Also put id's and names on your input elements, that way you can access them much easier.

Assuming you have an HTML like this :
<form>
<input type="text" id="text" />
<input type="submit" id='submit' value="clear above field without reloading" />
</form>
And you want the text field value to clear when a user submits without reloading using jQuery, then following script will be your remedy :
$(function(){
$('#submit').click(function(){
$('#text').value('');
})
});

A form can be submitted in many ways, not only by clicking on a submit buttons. You should really watch for submit events, and cancel them with preventDefault (instead of click events that might trigger the submit). See #user1359163's answer.
But you problem seem to be document.contact_form.name.value. There is no property contact_form on the document object, so this will raise an error. The preventDefault is not executed, your form gets submitted and you never see the error. Set your debugger to "Stop on errors"!
You might want something like document.forms["contact"], but I don't know your HTML. An id selector for the input element would be the better choice.

Page Redirection

I'm working on a script where all I want it to do (right now) is redirect the user based on which button they press. Eventually it will take form input and incorporate that into the redirect, but right now I'm just trying to get the buttons to send the user off to the appropriate site. However, My redirects aren't working.
<html>
<head>
<title>
Home
</title>
</head>
<body>
<script type="text/javascript">
<!--
var textstring;
var btnWhichButton;
//Gets the text from the form
function getQ() {
textstring = document.forms['Search'].elements[0].value;
}
//Does a Google Search
function googleSearch() {
window.location ="http://www.google.com";
}
//Does a YouTube Search
function youtubeSearch() {
window.location = "http://youtube.com";
}
//Figure out which button was pressed
function whichButton() {
if (btnWhichButton.value == 'Google Search' ) {
googleSearch();
} else if (btnWhichButton.value == 'YouTube Search' ){
youtubeSearch();
}
}
//main function to run everything
function main() {
getQ();
whichButton();
}
// -->
</script>
<form name="Search" >
<input type="text" name="q" size="31" maxlength="255" value="" />
<input type="submit" value="Google Search" onclick="btnWhichButton=this; main();" />
<input type="submit" value="YouTube Search" onclick="btnWhichButton=this; main();" />
</form>
</body>
</html>
When either button is clicked, the page just reloads with ?q= appended to the url, it doesn't redirect. Any help?

You want to use a button not an input type='submit'. Your current buttons are submitting the form, not performing their onclick actions.
Or block the submit action in some way. Or you could use your functions to set the form action to the url and just let it submit.

Your scripts seem highly overcomplicated. Why not have three functions: getQ, googleSearch, and youTubeSearch? Then inside the onClick event you can call the exact function, including this.value inside the input parameters and calling getQ from inside that function? Your method seems highly inefficient. If you're going to have separate functions for each of them anyways, there's no use in going through two other functions in order to get to them.
A submit button will always submit the form without a return false at the end of the onClick event, and since the default posting method is GET, its attaching ?q= to the end of your URL because that field is blank and it's the only input field in the form.

For redirecting to new page you no need to use the big javascript function.
<html> <body>
<input type="button" value="Google Search" onclick="javascript:window.location.href='http://www.google.com'" />
<input type="button" value="You tube Search" onclick="javascript:window.location.href='http://youtube.com'" />
</body></html>
Please check whether it helps you.

Well as jasonbar says, change your input to be of type 'button' and not 'submit'. Plus, I'd rather use window.location.href instead of window.location only. I don't know possible this is good practice...happy programming.

submit text field on enter press (AJAX)

I have a search that operates by AJAX. It works perfectly well when the user presses the search button, the problem is... if the user presses enter... it submit the form rather than executing the AJAX javascript function. How can I make the Enter button call my AJAX function as opposed to submitting the form?

Use the form's onsubmit event to execute your ajax call and make the button into a submit button if it isn't already.
Example HTML
<form action="/search.php" onsubmit="submitAjaxQuery(event)">
<input type="text" name="keywords" />
<button type="submit">Go!</button>
</form>
Example JS
function submitAjaxQuery(event)
{
if (event.preventDefault)
event.preventDefault();
else
event.cancel = true;
// run ajax calling function here.
}

Here is a simple DOM way to handle this:
<form action="javascript:void(0)">
<input type="text" />
<input type="submit" onclick="doSomething(this.form)">
</form>
<script>
function doSomething(form){
alert('form submitted');
}
</script>
Place the cursor in the input field, and either if you click the button or type enter, the form is submitted by javascript (not the page)

Trap it in the onSubmit method of the form and return false.

With jQuery:
jQuery("#myform").submit(function() {
callAJAXFunction();
return false;
});

The correct way is to let the non-javascript users use the form submit with page refresh but a javascript call for those with javascript:
<form action="yourscript.php" method="post" onsubmit="doSomething(this.form); return false;">
<input type="text" />
<input type="submit" />
</form>
<script>
function doSomething(form){
alert('form submitted');
}
</script>