JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
    <div class="row">
        <div class="col-lg-12 col-md-12 col-sm-12">
            <form class="form-inline" role="form">
                <div class="btn-group" role="group" aria-label="...">
                    <button type="button" class="btn btn-default">Default</button>
                    <button type="button" class="btn btn-primary">Primary</button>
                    <button type="button" class="btn btn-success">Success</button>
                    <button type="button" class="btn btn-info">Info</button>
                    <button type="button" class="btn btn-warning">Warning</button>
                    <button type="button" class="btn btn-danger">Danger</button>
                </div>

                <div class="input-group">
                    <input type="text" class="form-control" aria-label="...">
                        <div class="input-group-btn">
                        <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Action <span class="caret"></span></button>
                    </div><!-- /btn-group -->
                </div><!-- /input-group -->
            </form>
        </div><!-- /.col-lg-12 -->
    </div><!-- /.row -->

CSS

.btn-group {
        display: inline !important;
}
.form-inline .input-group {
    display: flex;
}
.form-inline .input-group .input-group-btn {
    display: flex;
}