discourse/app/assets/javascripts/discourse/components/login-modal.js.es6

export default Ember.Component.extend({
  didInsertElement() {
    this._super(...arguments);

    const prefillUsername = $("#hidden-login-form input[name=username]").val();
    if (prefillUsername) {
      this.set("loginName", prefillUsername);
      this.set(
        "loginPassword",
        $("#hidden-login-form input[name=password]").val()
      );
    } else if ($.cookie("email")) {
      this.set("loginName", $.cookie("email"));
    }

    Ember.run.schedule("afterRender", () => {
      $(
        "#login-account-password, #login-account-name, #login-second-factor"
      ).keydown(e => {
        if (e.keyCode === 13) {
          this.sendAction();
        }
      });
    });
  },

  mouseMove(e) {
    this.set("screenX", e.screenX);
    this.set("screenY", e.screenY);
  }
});