<!-- 歌词区 -->
          <scroll
            class="middle-r"
            ref="lyricScrollRef"
            :style="middleRStyle"
          >
            <div class="lyric-wrapper">
              <!-- 有歌词 --> ⬇️ 这里的 currentLyric 
              <div v-if="currentLyric" ref="lyricListRef">
                <p
                  class="text"
                  :class="{'current': currentLineNum === index}"
                  v-for="(line,index) in currentLyric.lines"
                  :key="line.num"
                >
                  {{line.txt}}
                </p>
              </div>
              <!-- 无歌词纯音乐 -->
              <div class="pure-music" v-show="pureMusicLyric">
                <p>{{pureMusicLyric}}</p>
              </div>
            </div>
          </scroll>

currentLyric 用于 v-if 判断，我的理解它在纯音乐和有歌词的情况都是有值的吧？是怎么判断 true/false 的，请老师点明？