Validating input fields form vue

**I wonder how can I run the emit in the App.vue file if all of the input fields of a multistep form are filled? I’ve written the logic but I can’t get the final block displayed in the end when all of the fields are filled.

https://codesandbox.io/s/intelligent-jasper-teh1im?file=/src/components/Button.vue

<template>
  <button class="btn" @click="submit">Submit</button>
</template>

<script>
export default {
  methods: {
    submit() {
      if (
        this.firstName !== "" &&
        this.lastName !== "" &&
        this.paymentAmount !== "" &&
        this.accountNumber !== ""
      ) {
        this.$emit("final");
      } else {
        alert("please fill the required fields");
      }
    },
  },
};
</script>

<style scoped>
.btn {
  padding: 10px 30px;
}
</style>

**