Accessing SVG file directly from Javascript code

Question

I have this HTML code, which is invoking my javascript code. The code is for a gauge. In the javascript code, I am trying to access a SVG file, and modifying the needle (of the gauge) to display the desired value. The code is working fine. However, I do not wish to call "object id" in HTML. I want to access SVG file through javascript directly, instead of using object id in HTML. I tried using el.setAttribute('data', 'gauge.svg'); But then svg_doc isn't able to retrieve the SVG image and modify the needle. Any help would be highly appreciated.

PS : I tried my best to be as thorough in explaining the problem. However, please let me know if I am unclear somewhere.

This is Gauge.png image which is embedded in the svg code I have pasted below https://sphotos-b.xx.fbcdn.net/hphotos-snc6/179594_10150982737360698_1827200234_n.jpg

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
    <g name="gauge" width="122px" height="127px">
        <image xlink:href="gauging.png" width="122" height="127"/>
    <circle id="led" cx="39" cy="76" r="5" style="fill: #999; stroke: none">
        <animateColor id="ledAnimation" attributeName="fill" attributeType="css" begin="0s" dur="1s"
        values="none;#f88;#f00;#f88;none;" repeatCount="0"/>
    </circle>
        <g id="needle" transform="rotate(0,62,62)">
            <circle cx="62" cy="62" r="4" style="fill: #c00; stroke: none"/>
            <rect transform="rotate(-130,62,62)" name="arrow"  x="58" y="38" width="8" height="24" style="fill: #c00; stroke: none"/>
            <polygon transform="rotate(-130,62,62)" points="58,39,66,39,62,30,58,39" style="fill: #c00; stroke: none"/>
        </g>
        <text id="value" x="51" y="98" focusable="false" editable="no" style="stroke:none; fill:#fff; font-family: monospace; font-size: 12px"></text>
    </g>
</svg>

HTML+Javascript code

    <head>
    <title>SVG Gauge example</title>

    <script>
    function update1(){
        var scale=100;
        var value;
        var value1 = 69;

        var el=document.getElementById('gauge1');       
        if (!el) return;

        /* Get SVG document from HTML element */
        var svg_doc = el.contentDocument;
        if (!svg_doc) return;


        /* Rotate needle to display given value */
        var needle_el = svg_doc.getElementById('needle');
        if (!needle_el) return;
        /* Calc rotation angle (0->0%, 260->100%) */
        value = parseInt(value1);
        scale = parseInt(scale);
        if (value > scale) value = scale;
        var angle = value / scale * 260;
        /* On-the-fly SVG transform */
        needle_el.setAttribute('transform','rotate('+angle+',62,62)');
    }
document.addEventListener('load', update1, true);
    </script>

    </head>

<div>
<object id="gauge1" type="image/svg+xml" data="gauge.svg" width="127" height="122"/>
</div>


</html>

I'm not really sure why you're so offended by this current method, this is how you do it. I've no idea what you mean by "object id"? If you don't want any HTML involved put the JS directly into the SVG. — robertc
– robertc, Commented Jul 30, 2012 at 22:18
If you look at the html code, you will see that I am using "gauge1" as object id which is referring to my main image "gauge.svg". there is nothing like I am offended, and I could explain you in great detail about the implications of using object id reference in html for my project. Anyhow, any feedback on solving my problem would be highly appreciated. — SandBag_1996
– SandBag_1996, Commented Jul 30, 2012 at 22:28
It isn't a problem, that's how it's supposed to work, there's nothing to 'solve'. If you have some special requirements that mean you can't do it this way then you'd better state those requirements in your question. — robertc
– robertc, Commented Jul 31, 2012 at 0:05
Okay. My requirement is that I want to access SVG file using Javascript only. I will remove HTML completely. Is it possible to access and modify SVG file, only using JS for the above code. — SandBag_1996
– SandBag_1996, Commented Jul 31, 2012 at 15:01

Yogu · Accepted Answer · 2012-07-31 20:13:02Z

As robertc already mentioned, you can embed the javascript code into your SVG file:

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
    <g name="gauge" width="122px" height="127px">
        <image xlink:href="gauging.png" width="122" height="127"/>
    <circle id="led" cx="39" cy="76" r="5" style="fill: #999; stroke: none">
        <animateColor id="ledAnimation" attributeName="fill" attributeType="css" begin="0s" dur="1s"
        values="none;#f88;#f00;#f88;none;" repeatCount="0"/>
    </circle>
        <g id="needle" transform="rotate(0,62,62)">
            <circle cx="62" cy="62" r="4" style="fill: #c00; stroke: none"/>
            <rect transform="rotate(-130,62,62)" name="arrow"  x="58" y="38" width="8" height="24" style="fill: #c00; stroke: none"/>
            <polygon transform="rotate(-130,62,62)" points="58,39,66,39,62,30,58,39" style="fill: #c00; stroke: none"/>
        </g>
        <text id="value" x="51" y="98" focusable="false" editable="no" style="stroke:none; fill:#fff; font-family: monospace; font-size: 12px"></text>
    </g>

    <script type="text/javascript">
        var scale=100;
        var value;
        var value1 = 69;

        /* Rotate needle to display given value */
        var needle_el = document.getElementById('needle');
        /* Calc rotation angle (0->0%, 260->100%) */
        value = parseInt(value1);
        scale = parseInt(scale);
        if (value > scale) value = scale;
        var angle = value / scale * 260;
        /* On-the-fly SVG transform */
        needle_el.setAttribute('transform','rotate('+angle+',62,62)');

    </script>
</svg>

I've put the code below the actual SVG contents so that the document is already loaded when the script is executed.

Then, you can view the SVG file directly e.g. in Firefox (I've tested it right now).

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