Elt.lang = 'fr' Not Working

I work in the context of a Firefox extension. Issue I'm trying to create a new element with a specific lang attribute. I tried the method elt.lang = 'zh' given in How to create HT

Solution 1:

Not all possible HTML attributes are reflected as javascript setters / getters. For instance, https://developer.mozilla.org/en-US/docs/Web/API/Node definitely lists textContent, but not lang. I would suggest always using setAttribute / getAttribute, except for possibly the most basic attributes such as "src" or "href".

Solution 2:

Issue

The problem was related to the environment (i.e. an extension). I was in a XUL context so using createElement() create a XUL element which don't have a lang attribute.

So to fix problem and other (no way to select inserted text), I had to force the XHTML namespace with createElementNS(ns, elt).

Code

var nsXHTML = "http://www.w3.org/1999/xhtml";
var wrapper = document.createElementNS(nsXHTML, "span");
var zh = document.createElementNS(nsXHTML, "i");
zh.lang= "zh-cmn";