Ejemplo tenemos la siguiente estructura html y deseamos eliminar la clase btn-primary sineliminar btn
<button class="btn btn-primary" type="button">Primary</button>
<button class="btn btn-secondary" type="button">Secondary</button>
<button class="btn btn-success" type="button">Success</button>
<button class="btn btn-danger" type="button">Danger</button>
<button class="btn btn-warning" type="button">Warning</button>
<button class="btn btn-info" type="button">Info</button>
<button class="btn btn-light" type="button">Light</button>
<button class="btn btn-dark" type="button">Dark</button>
<button class="btn btn-link" type="button">Link</button>$(this).removeClass(function (index, className) {
return (className.match (/(^|\s)btn-\S+/g) || []).join(' ');
});