Q:

How to execute a function after modal open?

I have added a Bootstrap Wizard inside the modal, and I need to initialize the Wizard only when this actually exists on the DOM 'cause I have to calculate the width, when the modal is closed if I execute:
$('.card-wizard').width()

I get: 0, when the modal is opened if I execute the same command above I get 465. The problem is that I have to calculate the width after that the modal is opened otherwise the width() method will return 0.
What I tried so far is:
$('a[href="#account"]').on('shown.bs.tab', function(){
    $('.card-wizard').bootstrapWizard({
         onInit: function(tab, navigation, index){
            let width = $('.card-wizard').width();
         }
    });
});

the tab is defined in that way:
<div class="wizard-navigation">
    <ul class="nav nav-pills">
        <li class="nav-item">
            <a class="nav-link active" href="#account" data-toggle="tab" role="tab">
                Account
            </a>
        </li>

and the wizard is contained inside the member-modal which is opened using $('#member-modal').modal('show');
is there a way to initialize the BootStrap Wizard after the modal show?

A:

The width is 0 because your element is inside the modal that is hidden.
You can workaround using .show( complete  ).
The snippet:

$('#exampleModal').show('show', function() {
    var x = $('.wizard').width();
    $('#exampleModal').hide();
    console.log('width: ' + x);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://www.bootstrapwizard.com/demo/bootstrap-wizard.css">
<script src="http://www.bootstrapwizard.com/demo/bootstrap-wizard.min.js"></script>


<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel"
     aria-hidden="true">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body wizard">
                <ul class="nav nav-wizard">
                    <li>
                        <a href="#step1">Step 1</a>
                    </li>
                    <li>
                        <a href="#step2">Step 2</a>
                    </li>
                    <li>
                        <a href="">Step 3</a>
                        <ul class="nav nav-wizard">
                            <li>
                                <a href="#step3a">Step 3A</a>
                            </li>
                            <li>
                                <a href="#step3b">Step 3B</a>
                            </li>
                            <li>
                                <a href="#step3c">Step 3C</a>
                            </li>
                        </ul>
                    </li>
                    <li>
                        <a href="#step4">Step 4</a>
                        <ul class="nav nav-wizard">
                            <li>
                                <a href="#step4a">Step 4A</a>
                            </li>
                            <li>
                                <a href="#step4b">Step 4B</a>
                            </li>
                            <li>
                                <a href="#step4c">Step 4C</a>
                            </li>
                        </ul>
                    </li>
                    <li>
                        <a href="#step5">Step 5</a>
                    </li>
                </ul>

                <div class="wizard-pane" id="step1">
                    <h3>Step 1</h3>
                </div>

                <div class="wizard-pane" id="step2">
                    <h3>Step 2</h3>
                </div>

                <div class="wizard-pane" id="step3a">
                    <h3>Step 3A</h3>

                    <p>Step 3 href is empty, so the first child is selected</p>
                </div>

                <div class="wizard-pane" id="step3b">
                    <h3>Step 3B</h3>
                </div>

                <div class="wizard-pane" id="step3c">
                    <h3>Step 3C</h3>
                </div>

                <div class="wizard-pane" id="step4">
                    <h3>Step 4</h3>
                </div>

                <div class="wizard-pane" id="step4a">
                    <h3>Step 4A</h3>
                </div>

                <div class="wizard-pane" id="step4b">
                    <h3>Step 4B</h3>
                </div>

                <div class="wizard-pane" id="step4c">
                    <h3>Step 4C</h3>
                </div>

                <div class="wizard-pane" id="step5">
                    <h3>Step 5</h3>
                </div>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                <button type="button" class="btn btn-primary">Save changes</button>
            </div>
        </div>
    </div>
</div>

