javascript - slider HTML5 起始位置之前/之后

Question

我最近遇到了 this before/after slider在 codepen.io 上。

但我有一个问题:如何更改 slider 开始的位置。 slider 从中间开始，我看不到这段代码中设置的位置:

function trackLocation(e) {
  var rect = videoContainer.getBoundingClientRect(),
      position = ((e.pageX - rect.left) / videoContainer.offsetWidth)*100;
  if (position <= 100) { 
    videoClipper.style.width = position+"%";
    clippedVideo.style.width = ((100/position)*100)+"%";
    clippedVideo.style.zIndex = 3;
    }
}
var videoContainer = document.getElementById("video-compare-container"),
videoClipper = document.getElementById("video-clipper"),
clippedVideo = videoClipper.getElementsByTagName("video")[0];
videoContainer.addEventListener( "mousemove", trackLocation, false); 
videoContainer.addEventListener("touchstart",trackLocation,false);
videoContainer.addEventListener("touchmove",trackLocation,false);

Answer 1

在CSS的底部

#video-clipper video {
  width: 450%;
  postion: absolute;
  height: 100%;
  }

https://codepen.io/anon/pen/jwMwXB