Storing data alongside DOM elements

Our code works, but it is quite slow. The culprit is the comparator function, which is performing a fair amount of work. This comparator will be called many times during the course of a sort, which means that every extra moment it spends on processing will be magnified.

Tip

Array sorting performance

The actual sort algorithm used by JavaScript is not defined by the standard. It may be a simple sort like a bubble sort (worst case of Θ(n2) in computational complexity terms) or a more sophisticated approach like quick sort (which is Θ(n log n) on average). It is safe to say, though, that doubling the number of items in an array will more than double the number of times the comparator function is called.

The remedy for our slow comparator is to pre-compute the keys for the comparison. We can do most of the expensive work in an initial loop and store the result with jQuery's .data() method, which sets or retrieves arbitrary information associated with page...