Restrict user to enter more than 16 digits in textbox

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Javascript

HTML

jQuery

In HTML form, there are four fields: first name, last name, credit card, cvv.

<div class="form-group">
                      <div class="col-sm-6">
                          <div class="input text"><label for="PlanFirstname">First name on Account</label><input name="data[Plan][firstname]" class="form-control" pattern="^[a-zA-Z\s]+$" title="Only alphabets and space are allowed" required="" type="text" id="PlanFirstname"></div>
                      </div>
                      <div class="col-sm-6">
                          <div class="input text"><label for="PlanLastname">Last name on Account</label><input name="data[Plan][lastname]" class="form-control" pattern="^[a-zA-Z]+$" title="Only alphabets are allowed" required="" type="text" id="PlanLastname"></div>                     </div>
                </div>
                <div class="form-group">
                     <div class="col-sm-6">

                    <div class="input text"><label for="PlanCardnumber">Card number (no dashes or spaces)</label><input name="data[Plan][cardnumber]" class="form-control" pattern="[0-9]{16}" title="16 digits" required="" type="text" id="PlanCardnumber"></div>                 </div>
                    <div class="col-sm-6">
                    <div class="input text"><label for="PlanCvvnumber">cvv number</label><input name="data[Plan][cvvnumber]" class="form-control" pattern="[0-9]{3,4}" title="3 to 4 digits" required="" type="text" id="PlanCvvnumber"></div>                  </div>
                </div>

For each field, required validation has been applied using required attribute and regular expression has been applied to each field using "pattern" attribute.
I want that user should not able to enter any digit after 16 digits in credit card number textbox. Validation has been applied for maximum 16 digits, but user is able to enter more than 16 digits and validation message is shown to user on submit button click. How to restrict user to enter more than 16 digits?