kek

js
    <script>
        let form = document.getElementsByTagName('form')[0];
        let token = document.getElementsByName('csrf_token')[0].value;
        form.addEventListener('submit',(e) => {
            let request = new XMLHttpRequest();
            request.open('POST', '/auth/singup_validate', false)
            request.setRequestHeader("X-CSRFToken", token)
            request.send()
            console.log(request.response)
            e.preventDefault();
        })
    </script>

flask

@blueprint.route('/singup_validate', methods=['POST'])
def singup_validate():
    form = SingUpForm()
    print(request.headers)
    if form.validate_on_submit():
        return jsonify(data={'status': True})
    return jsonify(data=form.errors)