in src/CSSTransition.js [207:225]
removeClasses(node, type) {
const {
base: baseClassName,
active: activeClassName,
done: doneClassName,
} = this.appliedClasses[type];
this.appliedClasses[type] = {};
if (baseClassName) {
removeClass(node, baseClassName);
}
if (activeClassName) {
removeClass(node, activeClassName);
}
if (doneClassName) {
removeClass(node, doneClassName);
}
}