How to access data in vue cli?

Question

Vue.js

Hello, in vue cdn to get a variable from data it was enough to use this.myVariable
but for some reason this does not work in vue cli

<script>
export default {
  name: "Auth",
  data() {
    return {
      page: 0,
    };
  },
  methods: {
    selectPage(number) {
      this.page = number; //пишет что this == undefined
    },
  },
  directives: {
  },
};
</script>