Obtaining an original SVG viewBox via javascript

Question

Our system loads SVG files programmatically into HTML via AJAX. A typical SVG file begins with:

 <svg xmlns='http://www.w3.org/2000/svg' viewBox='0,0 65415,41616' xml:space='preserve' height='50.000cm'  width='50.000cm' xmlns:xlink='http://www.w3.org/1999/xlink

But strangely in JavaScript there seems to be no way of getting this 'viewBox' back from the SVG DOM - either as a string, or as a set of values. Under Mozilla, for example, firebug reports that the svg node has 5 of the 6 attributes we specifiy - namely: xmlns, xml:space, height, width and xmlns:xlink. But ViewBox is conspicuously missing from this list.

Is there anyway to programmatically retrieve this value? - where is it in the SVG DOM? (We cannot introduce 3rd party libraries).

Answer 1

Even easier, put an id in your svg then :

document.getElementById("your_id").getAttribute("viewBox");

Answer 2

You'll want to take a look at the SVGFitToViewBox interface, which specifies the viewBox property. The interface for svg elements, SVGSVGElement, extends that interface, so that might be the property you're looking for.

Answer 3

Above receipes gave me all zeros for the x, y, width and height viewBox attributes -- unless at least one of them was changed programmatically.

I finally succeded with

var width = document.getElementById("mysvg").getAttribute("width");

Answer 4

1. Go to http://phrogz.net/SVG/svg_in_xhtml5.xhtml
2. Open your web browser console

3. Type the code:

   var svg = document.querySelector('svg');
   var box = svg.getAttribute('viewBox');
   box.split(/\s+|,/);
   

4. Observe the glorious response:

   ["-350", "-250", "700", "500"]
   

5. Alternatively, type the code:

   var box = svg.viewBox.baseVal;
   [ box.x, box.y, box.width, box.height ]
   

6. Observe the glorious response:

   [ -350, -250, 700, 500 ]
   

In other words: yes, you can get the viewBox from the DOM, both as a standard DOM 2 attribute as well as an explicit ECMASCript binding.