VueTube/NUXT/components/Player/seekbar.vue

<template>
  <v-progress-linear
    active
    background-color="primary"
    background-opacity="0.5"
    :buffer-value="buffered"
    color="primary"
    height="3"
    query
    :value="percentage"
  />
</template>

<script>
export default {
  props: ["video"],

  data() {
    return {
      percentage: 0,
      buffered: 0,
    };
  },

  mounted() {
    this.video.ontimeupdate = () => {
      this.percentage = (this.video.currentTime / this.video.duration) * 100;
    };
    this.video.addEventListener("progress", () => {
      this.buffered = (this.video.buffered.end(0) / this.video.duration) * 100;
    });
  },
};
</script>