direction: rtl;

.outer-div {
  width:70%;
  margin-left:auto;
  margin-right:auto;
  text-align:right;
  overflow:hidden;
  white-space: nowrap;
}

.inner-div {
  float:right;
}

:

<div class="outer-div">
  <div class="inner-div">
    <p>A very long line that should be trimmed on the left</p>
  </div>
</div>

<div style="width: 65px; height: 20px;
            overflow: hidden; position: relative; background: #66FF66;">
    <span style="position: absolute; right: 0;">05451234567</span>
</div>

<div style="direction: rtl;">
  <span style="white-space: nowrap; direction: ltr; display: inline-block;">your short or long comment<span>
</div>

<div id="outer-div">

    <p>ipsum dolor amet bacon venison porchetta spare ribs, tongue turducken alcatra doner leberkas t-bone rump ball tip hamburger drumstick. Shoulder strip steak ribeye, kielbasa fatback pig kevin drumstick biltong pork short loin rump. Biltong doner ribeye, alcatra landjaeger tenderloin drumstick t-bone pastrami andouille. Sirloin spare ribs fatback, bresaola strip steak alcatra landjaeger kielbasa cupim doner. </p>

</div>

#outer-div {
  width:100%;
  margin-left:auto;
  margin-right:auto;
  text-align:right;
  overflow:hidden;
  white-space: nowrap;
  border:1px solid black;
}

let outer = document.getElementById("outer-div");
outer.scrollLeft += outer.scrollWidth;