Parse SVG transform attribute with javascript

Question

Supposing we have an SVG transform string:

transform = "translate(6,5),scale(3,3)";

Is there a slick regex function we could use to parse that into something usable?

Answer 1

Here's a nifty little snippet of code that might get you what you need, it should cover most scenario in case the string you intend to parse has different number of arguments:

function parse (a)
{
    var b={};
    for (var i in a = a.match(/(\w+\((\-?\d+\.?\d*e?\-?\d*,?)+\))+/g))
    {
        var c = a[i].match(/[\w\.\-]+/g);
        b[c.shift()] = c;
    }
    return b;
}

Running this

parse('translate(6,5),scale(3,3.5),a(1,1),b(2,23,-34),c(300)');

Will result in this:

{
    translate: [ '6', '5' ],
    scale: [ '3', '3.5' ],
    a: [ '1', '1' ],
    b: [ '2', '23', '-34' ],
    c: [ '300' ]
}

Answer 2

Assuming you are running in a browser, you could also use the SVG DOM to parse and decode the transform string.

var svgns = "http://www.w3.org/2000/svg";

function getTransformList(transformStr)
{
  // Create a fake <rect> element to set the transform to
  var rect = document.createElementNS(svgns, "rect");
  rect.setAttribute("transform", transformStr);
  // Use the DOM to get the list of decoded transforms
  dumpTransform(rect.transform.baseVal);
}

function dumpTransform(transformList)
{
  for (var i = 0; i < transformList.numberOfItems; i++)
  {
    var transform = transformList.getItem(i);
    var m = transform.matrix;
    switch (transform.type)
    {
      case 2:
        console.log("translate("+m.e+","+m.f+")");
        break;
      case 3:
        console.log("scale("+m.a+","+m.d+")");
        break;
      case 4:
        console.log("rotate("+transform.angle+")");
        // TODO need to also handle rotate(angle, x, y) form
        break;
      case 5:
        // TODO skewX()
        break;
      case 6:
        // TODO skewY(()
        break;
      case 1:
      default:
        console.log("matrix("+m.a+","+m.b+","+m.c+","+m.d+","+m.e+","+m.f+")");
        break;
    }
  }
}

getTransformList("translate(6,5),scale(3,3)");

Answer 3

Adapted from @chernjie's solution:

function parse_transform(a) {
    var b = {};
    for (var i in a = a.match(/(\w+)\(([^,)]+),?([^)]+)?\)/gi)) {
        var c = a[i].match(/[\w\.\-]+/g);
        b[c.shift()] = c;
    }
    return b;
}

Answer 4

var transform = "translate(6,5),scale(3,3)";
var translate  = /translate\(\s*([^\s,)]+)[ ,]([^\s,)]+)/.exec(transform);
var translateX = translate[1]
var translateY = translate[2]
var scale  = /scale\(\s*([^\s,)]+)[ ,]([^\s,)]+)/.exec(transform);
var scaleX = translate[1]
var scaleY = translate[2]

transformValues = {translate:{x:translateX,y:translateY},
scale:{x:scaleX,y:scaleY}}

Pretty gross, but @icedwater was making me do all the work myself so...