Two different views of the same svg drawing

Question

I want to make a fairly large diagram using SVG (I have been using Snap.svg in JavaScript). I'd like to display a zoomable portion of the diagram in an element, and also a smaller version of the whole thing in a different element, in which the user can navigate.

One strategy is this:

Make two identical SVGs, except that they have different viewBoxes, and every time I change one of the svg elements, make an identical change to the other copy. The viewBox attributes cause each view to show the right part of the diagram.

Is that a good strategy? Seems fragile and wasteful to me. Is there some other, smarter approach? Do I really have to draw everything twice?

Hoping for "D'oh!"

Answer 1

Yes it's possible to have a master SVG and then "thumbnail" and/or "zoomed" versions of the same image that update automatically.

document.getElementById("but").addEventListener("click", function() {
  var svg = document.getElementById("mainsvg");
  var c = document.createElementNS("http://www.w3.org/2000/svg", "circle");
  c.setAttribute("cx", 1000*Math.random());
  c.setAttribute("cy", 1000*Math.random());
  c.setAttribute("r", 50);
  c.setAttribute("fill", "red");
  svg.appendChild(c);
});

#main {
    width: 400px;
    height: 400px;
}

#thumb,
#zoom {
    display: inline-block;
    width: 80px;
    height: 80px;
}

svg {
  border: solid 1px grey;
}

<div id="main">
    <svg id="mainsvg" viewBox="0 0 1000 1000">
        <rect x="100" y="100" width="500" height="500" fill="green"
              transform="rotate(10,350,350)"/>
        <rect x="400" y="400" width="500" height="500" fill="orange"
              transform="rotate(-10,650,650)"/>
    </svg>
</div>


<div id="thumb">
    <svg xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 1000 1000">
        <use xlink:href="#mainsvg" />
    </svg>
</div>


<div id="zoom">
    <svg xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 1000 1000">
        <use xlink:href="#mainsvg" 
             x="-500" y="-1200"
             width="3000" height="3000" />
        <!-- control the zoom and position with x, y, width and height -->
    </svg>
</div>


<div>
  <button id="but">Click me</button>
</div>