Input value doesn't hold the value after clicking button - laravel

Question

I'm trying to type invoice number as input type i.e. 123456789
After I click Print Record button, the value of invoice number disappears like this:
Aslo I have wrote
<div class="form-group row">
<label for="invoice_no" class="col-sm-2 col-form-label">Inovice Number</label>
<div class="col-sm-10">
<input type="text" class="form-control col-sm-4" name="InvNumber" id="InvNumber" value="{{request()->input('InvNumber')}}">
</div>
</div>
And the Print button looks like:
<div class="form-group row">
<div class="col-sm-12 dol-12" >
<button class="btn btn-secondary float-right" onclick="printDiv()">Print Record</button>
</div>
And printDiv() function is:
<script type="text/javascript" language="javascript">
function printDiv(divName) {
var printContents = document.getElementById('printableArea').innerHTML;
document.body.innerHTML = printContents;
window.print();
}

Answer 1

Clicking a submit button will submit the form it is in.
Presumably, your form's action is the current URL, so it reloads the page.
The new page doesn't have the data in the form fields that you had typed into the previous page.
If you don't want to submit the form, use the type attribute to change the <button> from its default of submit.

Answer 2

As per the documenation, if you don't specify type of button it assumes it as submit button that is why your form is being submitted by default.
Add type="button" in your button
<button type="button" class="btn btn-secondary float-right" onclick="printDiv()">Print Record</button>
submit: The button submits the form data to the server. This is the
default if the attribute is not specified for buttons associated with
a form, or if the attribute is an empty or invalid value.
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button