Ran into a problem today with attempting to manipulate textPath SVG elements within the DOM. Consider the following, where the variable svg is an SVG element in your DOM:
var g = document.createElementNS("http://www.w3.org/2000/svg", "g");
var label_container = document.createElementNS("http://www.w3.org/2000/svg", "text");
var label = document.createElementNS("http://www.w3.org/2000/svg", "textPath");
label.setAttributeNS("http://www.w3.org/1999/xlink", 'xlink:href', '#some-path');
label.appendChild(document.createTextNode("Hello, World!"));
label_container.appendChild(label);
g.appendChild(label_container);
svg.appendChild(g);
If you specify a path for your textPath node (in red, above), you’ll need to use the setAttributeNS function (as opposed to the setAttribute function, as one (i.e. me) could mistakenly use).
In addition, when attempting to query the DOM for the textPath element, ensure you create your textPath elements with the proper case and your query selectors are case sensitive in WebKit browsers:
document.querySelector('textPath');
As an FYI, textPaths are used to provide a path for which your text will follow. For example, if you wanted to show some text radially about a circle. The xlink property is used to specify which textPath that is defined will be used for a given text node. Check out w3.org.