Read Attributes of SVG-Elements in HTML via JS

问题

I have the following markup (HTML with native SVG):

<!doctype html>
   <!-- ...    
        html-Elements 
        ... --> 
   <svg version="1.1" ... >
        <defs> <circle id="infop" cx="0" cy="0" r="9" /> </defs>
        <!-- ... 
             svg Elements
             ... --> 
        <svg> <!-- to have separate coordinate-system -->
            <g id="outSvg"></g>
        </svg>
    ...

A js-method outputs a line and several <use href="infotop"> Elements to #outSvg (to become a graph). The <use> Elements have onmouseover-Events to show tooltips.

Now, when it comes to retrieving the coordinates in the onmouseover-function of the <use> i run into problems:

I tried the following different approaches to retrieve the values:

function showInfo(evt){

    console.log("target: "+evt.target);
    console.log("AttrNS: "+evt.target.getAttributeNS(null,"x"));
    console.log("Attrib: "+evt.target.getAttribute("x"));
    console.log("basVal: "+evt.target.x.baseVal.value);
    console.log("corrEl: "+evt.target.correspondingUseElement.x.baseVal.value);

producing the following output:

    //target -> ** [object SVGUseElement] in FF, in all other browsers: [object SVGElementInstance])
    //AttrNS -> Works only in FF
       // * Uncaught TypeError: Object #<SVGElementInstance> has no method 'getAttributeNS'
    //Attrib -> Works only in FF
       // * Uncaught TypeError: Object #<SVGElementInstance> has no method 'getAttribute'
    //basVal -> works only in FF
       // * Uncaught TypeError: Cannot read property 'baseVal' of undefined
    //corrEl -> fails in FF but works in Ch, O and IE

Browsers:FF10, Ch16, O11.61, IE9

Question:

Why is getAttribute() failing in the other browsers? Am I missing something important? Is there a consistent way to retrieve the values crossbrowser? (Besides via a switch between evt.target.x and evt.target.correspondingUseElement.x)

important: vanilla js only, and I know about browserswitches, thats not the point! I'll provide a fiddle if needed, as soon as i find the time. Finally - thank you for reading this!

EDIT: * added the js-errors

EDIT2: ** FF returns another Object than the other browsers

回答1:

Well, after reading Erik Dahlströms answer, i noticed that FF behaves wrong. It should return an Element-Instance instead of the Use-Element directly.

I use the following code now:

var el = (evt.target.correspondingUseElement)?evt.target.correspondingUseElement:evt.target;

console.log(el.getAttribute("x"));

This way i can retrieve the Attributes via getAttribute() consistently in all browsers.

回答2:

can you try this? evt.target.getAttributeNode("x").nodeValue . I tried this in safari,chrome,Firefox its working fine.

回答3:

As far as I know Firefox doesn't support SVGElementInstance.

Here are a couple of tests for SVGElementInstance from the w3c SVG 1.1 Second Edition testsuite to verify:

struct-dom-12-b
struct-dom-14-f
struct-dom-15-f

What you should do is to provide a fallback solution if the SVGElementInstance isn't there, which is easy enough to detect, e.g:

if (elm.correspondingUseElement) {
  /* elm is a used instance, not a real element */
} else {
  /* fallback solution */
}

If the element is an SVGElementInstance it will have the correspondingUseElement property, otherwise it won't have it. Normal svg elements will not have this property, only used instances will have it.

回答4:

Did you try evt.target.getAttributeNS(evt.target.parent.namespaceURI,"x") ?

来源：https://stackoverflow.com/questions/9275695/read-attributes-of-svg-elements-in-html-via-js

标签

javascript

cross-browser

svg

no-framework