DOMImplementation.hasFeature

The DOMImplementation.hasFeature() method returns a Boolean (en-US) flag indicating if a given feature is supported.

The different implementation fairly diverged in what kind of features was reported. The latest version of the spec settled to force this method to always return true, except for SVG features, where the functionnality was accurate and in use.

flag = document.implementation.hasFeature(feature, version);