SVG文本路径-动画化startOffset（向下滑动SVG路径的文本）-在JS中

Question

How can I animate the SVG textpath startOffset parameter in WebAnimation/JS (NOT CSS!):
I want to let the text slide down the path... I tried numbers , % , px with no success.

<svg id="text-on-path-svg" width="400" height="400"  style="border:1px solid #00f"> 
<path id="myPathforText" fill="none" stroke="#000" d="M90,90C90,160 250,160 300,300"/>
<text >
    <textpath id="slideText" xlink:href="#myPathforText" startOffset="50%" >Text laid out along a path.</textpath>
</text>

<script type="text/ecmascript">
  <![CDATA[

var slideText=document.getElementById("slideText");
var slideTextPlayer=slideText.animate(
     [{startOffset:'0%'},
      {startOffset:'100%'}],
     {duration:3000,delay:0,iterations:Infinity});
]]>
</script>
</svg>

JSFiddle: https://jsfiddle.net/509c8pmj/ Help would be much appreciated.

Answer 1

One way is by placing an animate element inside your textpath element, like this:

<textpath id="slideText" xlink:href="#myPathforText" startOffset="50%" >
    Text laid out along a path.
    <animate attributeName="startOffset" from="0%" to ="100%" begin="0s" dur="3s" repeatCount="indefinite"/>
</textpath>

You can use repeatCount="indefinite" if you want it to keep looping.

I've been learning some of the SVG + SMIL syntax from articles on https://css-tricks.com (but their site was down for me as I'm writing this.)