Writing Fast, Memory-Efficient JavaScript
> Never use delete. Ever....This is horrible advice. There are plenty of things you want to delete, like references to elements when you don't need them anymore. A quick search of the Closure Library, jQuery, Backbone, Knockout, Angular.js, and ember.js found many uses of delete. Burn this article in a fire.As for the supposed performance difference, let's see a jsperf on that.Edit found one:http://jsperf.com/delete-vs-undefined-vs-null/6Delete is a little slower, certainly not enough to warrant the 'never' emphasis.