javascript - 基本垂直 SVG 线

Question

我似乎无法找到一个好的、有效的示例/教程来说明如何绘制一条简单的垂直线，该线在滚动时从无到有逐渐动画化。

我有下面的代码绘制一条水平线，但我似乎无法成功地将其更改为一条继续动画的垂直线。

HTML:

<svg id="mySVG">
    <path fill="none" stroke="red" stroke-width="3" id="triangle" d="M1 0 L75 0"/>
</svg>

CSS:

#mySVG {
  position: fixed;
  top: 15%;
  width: 400px;
  height: 210px;
  margin-left:0px;
}

JS:

<script>
    // Get the id of the <path> element and the length of <path>
    var triangle = document.getElementById("triangle");
    var length = triangle.getTotalLength();

   // The start position of the drawing
   triangle.style.strokeDasharray = length;

   // Hide the triangle by offsetting dash. Remove this line to show the             triangle before scroll draw
   triangle.style.strokeDashoffset = length;

  // Find scroll percentage on scroll (using cross-browser properties), and offset dash same amount as percentage scrolled
  window.addEventListener("scroll", myFunction);

  function myFunction() {
      var scrollpercent = (document.body.scrollTop +      document.documentElement.scrollTop) / (document.documentElement.scrollHeight -    document.documentElement.clientHeight);

      var draw = length * scrollpercent;

     // Reverse the drawing (when scrolling upwards)
     triangle.style.strokeDashoffset = length - draw;
}
</script>

Answer 1

这应该只是让你的线垂直的问题，如下所示:

<svg id="mySVG">
  <path fill="none" stroke="red" stroke-width="3" id="triangle" d="M1 0 L1 75"/>
</svg>

当你这样做时会发生什么？