JavaScript - Feature Detection

javascript

// JavaScript - Feature detection versus Feature Inference:

Feature inference is less reliable than feature detection.  Feature inference
is making assumption that a particular feature is available based on another
feature is available or not.  For example, Chrome implements the Text function. 
I also know Chrome doesn’t have applyElement like IE does.
if(typeof applyElement != 'undefined') {
    // now I know I'm not in IE, I'll just assume Text is available
    text = new Text('Oh, how quick that fox was!');
}
Someone looked at that code in Firefox which doesn’t implement applyElement or 
Text! They got an error.