ha_permissions/ui/login/index.js

export default {
    form: null,

    display(){
        if(this.form === null){
            this.form = document.querySelector("#loginPage form");
            this.form.addEventListener("submit", (event)=>{
                this.submit(event);
            });
        }
    },

    submit(event){
        event.preventDefault();
        console.log("submitting");
    }
}