I found that the text ellipsis set in .inner_right does not work. After testing, I added overflow: hidden to the .left box, and the ellipsis appeared. how to explain this situation?
.box {
  height: 100px;
  width: 100%;
  display: flex;
}
.left {
  flex: 1;
  display: flex;
  background-color: blue;
  /* overflow: hidden;  It will not work without adding this */
}
.right {
  width: 200px;
  background-color: black;
}
.left .inner_left {
  width: 100px;
  background-color: antiquewhite;
}
.left .inner_right {
  flex: 1;
  background-color: aquamarine;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}<div class="box">
  <div class="left">
    <div class="inner_left"></div>
    <div class="inner_right">
      some text some text some text some text some text some text some text some text some text some text some text some text some text some text some text some text
    </div>
  </div>
  <div class="right"></div>
</div> 
    