methods.vue

<template>
  <!-- pass in the "like" variable that corresponds to the input-value by using v-model -->
  <form v-on:submit.prevent="onSubmit(like)">
    <label
      >What do you like:
      <input v-model="like" />
    </label>
    <input type="submit" />
  </form>
</template>

<script>
export default {
  methods: {
    onSubmit(thing = "turtles") {
      console.log(`I like ${thing}.`);
      // equivalent code that doesn't use an argument
      // console.log(`I like ${this.like ?? "turtles"}.`);
    },
  },
};
</script>