If the browser that you are planning to use is Mozilla (Addon development) (not sure of chrome) you can use the following method in Javascript
function DOM( string )
{
var {Cc, Ci} = require("chrome");
var parser = Cc["@mozilla.org/xmlextras/domparser;1"].createInstance(Ci.nsIDOMParser);
console.log("PARSING OF DOM COMPLETED ...");
return (parser.parseFromString(string, "text/html"));
};
Hope this helps