This is a drop-in replacement for the SVGPathSeg, SVGPathSegList, and getPathSegAtLength APIs that were removed from SVG2 (https://lists.w3.org/Archives/Public/www-svg/2015Jun/0044.html). Existing code that uses the SVGPathSeg or SVGPathSegList APIs can use this polyfill to keep working. This polyfill is based on the exact code and tests that were removed from Chromium 47.

The SVGPathSeg API was difficult to use and has been removed from the SVG spec in favor of a new, awesomer API in the Paths module (https://lists.w3.org/Archives/Public/www-svg/2015Jun/0044.html). All new development should use the SVG Path Data API. There's a polyfill (path-data-polyfill.js) for browsers that do not yet support the new API.

Now passing all SVGPathSeg tests from the Chromium repository.

Now used by svg-edit and passes all svg-edit path tests.

Blink will likely remove SVGPathElement.getPathSegAtLength (see: Intent to deprecate and remove SVGPathElement.getPathSegAtLength). A getPathSegAtLength polyfill has been added to this library.

Firefox 59 will likely remove portions of the SVGPathSeg and SVGPathSegList APIs (see: Remove the WebIDL methods for creating and mutating SVG path data). This library has support for polyfilling this partial implementation.

Just add pathseg.js to your server and drop this in your html or svg files:

<script src="pathseg.js"></script>

var path = document.createElementNS("http://www.w3.org/2000/svg", "path");
var moveToSeg = path.createSVGPathSegMovetoRel(10, 10);
var lineToSeg = path.createSVGPathSegLinetoRel(100, 100);
path.pathSegList.appendItem(moveToSeg);
path.pathSegList.appendItem(lineToSeg);
console.log(path.getAttribute('d')); // m 10 10 l 100 100
moveToSeg.x += 200;
moveToSeg.y += 200;
console.log(path.getAttribute('d')); // m 210 210 l 100 100

These APIs have been removed from SVG 2 but their original definitions can be found at:

http://www.w3.org/TR/SVG/single-page.html#paths-InterfaceSVGPathSeg

http://www.w3.org/TR/SVG/single-page.html#paths-InterfaceSVGPathSegList

https://www.w3.org/TR/SVG/single-page.html#paths-__svg__SVGPathElement__getPathSegAtLength