Develop Reference

Reading in Data from HTML Javascript form

I am creating a website backed by a database. I have created my forms that collect the information but now i need to read in the input from the form when user clicks submit and process it for mySQL. I am having my form action be a new page but I can't figure out how to read in value from the previous page. My Form code looks like this:
<div data-wrapper-react="true">
<span class="form-sub-label-container" style="vertical-align:top;">
<input type="text" id="first_3" name="q3_fullName3[first]" class="form-textbox validate[required]" size="10" value="" data-component="first" />
<label class="form-sub-label" for="first_3" id="sublabel_first" style="min-height:13px;"> First Name </label>
</span>
When user hits submit the action for this page is connect.php. I am not sure how to read in the value there. I tried this following command:
document.getElementById("first_3").value;
This just displays the code on blank html page for connect.php and not read in the values. The data from the forms needs to be processed into different tables if someone can help with that as well that would be great. Thanks

Form handling, in the way you are describing, is something you do server-side. PHP is handled on the server first where PHP tags can be evaluated to HTML, then this is returned to the browser. You would not handle form input from javascript, until after your PHP has done something with it. Here is a refresher: https://www.w3schools.com/php/php_forms.asp
<?php echo $_POST["q3_fullName3[first]"]; ?> would output the value into the HTML page allowing you to do something like this:
console.log("<?php echo $_POST["q3_fullName3[first]"]; ?>");
If you view source of the HTML, you will notice the PHP tag is gone and replaced with the form field value.
It sounds like you might want to get a book about PHP + MySQL since interacting with a database is a more advanced topic. I can recommend this one:
https://www.amazon.com/Learning-PHP-MySQL-JavaScript-Javascript-ebook/dp/B00QUBHNFI/ref=mt_kindle?_encoding=UTF8&me=

How would I go about changing the contents of a div after the user searches?

So I have this form:
<form method="post" action="index.php" id="searchform">
<input type="text" name="search" placeholder="Search...">
<input type="image" src="img/img1.png" alt="submit" onmouseover="hover(this);" onmouseout="unhover(this);" /></a>
</form>
When the user searches for something I want to change this div:
<div class = "mainText">
<h2>Today's Events: </h2>
</div>
To say this:
<div class = "mainText">
<h2>Results: </h2>
</div>
How can I do this?
EDIT: Is it possible to run this code from within a php if statement?

jquery .text() seems a better fit, so you can just change the text of the tag.
$(".mainText h2").text("Results:");
More on this here:
http://www.w3schools.com/jquery/html_text.asp

The action in your form is the destination of where your form ends up.
If you are looking to control the dom elements you need something like javascript or jquery to control the front end of your application.
You could use jquery to simply listen for when your user has clicked the button or submitted the form and parse the results (in this case, just switching html text). *Remove the the action destination otherwise the page will redirect to index.php
$('form').submit(function(){
$('.mainText').html('<h2>Results: </h2>');
return false;
});
Common usage is to put an ajax call in the submit function to retrieve some data from outside the page source. Hopefully that puts you on track :)

using Dropzone.js and php to show the contents of uploaded file to a textfield without refreshing the page

I am using dropzone.js to implement file upload. I am using it to make a web compiler. Using php/ajax I want to show the contents of the file in the editor text area without saving the file in the server.
My current code snippets are-
<form role="form">
<textarea id="editor">
<?php if( isset( $data['source'] ) )
echo $data['source']; ?></textarea>
</form>
` <form class="dropzone dz-clickable" action="upload.php" enctype='multipart/form-data'>
<i class="fa fa-cloud-upload element"></i>
<div style="color:gray;">Drag and drop or click to upload file</div>
<input type="hidden" name="filenameEmail" class="filenameEmail" value="">
<input type="hidden" name="side" value="front">
</form>`

with the bit of code provided it's a bit hard to get to a proper solution fitting your needs.
generally (and as you asked for only an idea of how you could do it) however, I'd go with using the success event from dropzone.js which provides the server response as the second parameter according to there Documentation.
So what you do is reading out the data from the uploaded file using your upload.php and returning it so you can use it in the told event.
Easiest way (as always) is using jQuery with it to have full control of the response and assign the provided text/code/whatever to the
$('#editor').val();

How to reference to an uploaded img src in HTML

I am creating a responsive mobile website, and I want to be able to take and then upload a picture from the device. I have got this part working using
<form method="post" action="takephoto.php" enctype="multipart/form-data">
<input type="file" id="myfile" name="myfile" accept="image/*;capture=camera"/>
</form>
Now, what I am having trouble with is, after I have selected the picture that I want to use I do not know how to reference it later in my code. The reason I need to is I am using a .js library which allows me to upload a picture of a ISBN barcode and the .js file will read this file and spit out the ISBN as text which I will do more with later. (maybe link this to a Google Books API)
This is where I am getting the barcode scanner .js from: http://badassjs.com/post/654334959/barcode-scanning-in-javascript
I am relatively new to all of this, thanks for your help.

You will have to use ajax. This link contains some useful information for you.
Use ajax to get the picture uploaded and in the response, return the url or "failed". Then you can use in your js code,
if(response=="failed"){
//Handle upload failed
}
else {
//Handle url. Here response is your url actually.
// So to append the image to a given id, you would use,
$("#append_to_id").append("<img src='"+response+"'>");
}

Since the JavaScript library you are using is parsing an image on the page,
you have to show the image on the page after you have uploaded it.
So basically you need 4 steps to achieve this:
show an upload form (This is what you have done in the question);
grab the image uploaded in step 1 and save it to an accessible place
display the image on the screen
call get_barcode_from_image.js to parse it
Here's a piece of code for reference. It contains all the 4 steps above.
<?php
// step 2: save the image
if ($_FILES['myfile']['error'] == 0) {
move_uploaded_file($_FILES['myfile']['tmp_name'], 'u/barcode.jpg');
?>
<!-- step 3: show the image -->
<img src="u/barcode.jpg" id="barcode">
<script src="get_barcode_from_image.js"></script>
<div id="result"></div>
<!-- step 4: parse the barcode -->
<button onclick='document.getElementById("result").innerHTML = getBarcodeFromImage("barcode")'>scan</button>
<?php
}
?>
<!-- step 1: show the upload form -->
<form method="post" action="barcode.php" enctype="multipart/form-data">
<input type="hidden" name='a' value='b'/>
<input type="file" id="myfile" name="myfile" accept="image/*;capture=camera"/>
<input type="submit" value="submit" />
</form>
Of course you can use ajax or so to get better user experience, but the process won't change.

Can an onsubmit event insert an image into the page before the page submits?

Can an onsubmit event insert an image into the page before the page submits/transfers control to the next page?
I am using classic asp.

Of course. The function resolves before the form is submitted.
(Although… while an img element may be inserted into the page, it might not load before the browser has gone to the next one, and even if it does, the user might not have time to see it clearly)

Yes . You can insert the HTML code (through javascript):
<img src="imgsrc">
But it takes a little time for loading the image. The form send the user to another page in new window or in the same window? Why would you want to insert an image in the current window if the page will be replaced with the new one?

Yes you can do this. It would be easier (for me to write) if you used jquery:
html:
<form id="myForm" action="">
<input type="text" id="someId" />
<input type="submit" id="submit" value="submit" />
</form>
and then JavaScript would be:
$(document).ready(function() {
$("#myForm").submit(function() {
$(this).append('<img src="someImage.jpg" alt="" />');
});
});
http://jsfiddle.net/rYUbQ/
But like others have said it might not be loaded and displayed before the form submits so you might want to instead look in to preloading the image and then just setting it to visible before the page submits.