It seems unlikely that an engine can ever make this prediction with sufficient confidence to justify investing this time and memory.Īs a rule of thumb: when operating on large data sets, choosing efficient algorithms and data structures is worth it. Aside from the difficulty of building such a system that works for arbitrary predicates, this technique even when it does work would only speed up repeated searches of the same array with the same function, at the cost of wasting time and memory if this exact same scenario will not occur again. In theory, since JS engines can do dynamic optimizations, they could inspect the predicate function, and if it has no side effects, they could use it to build up some sort of index/cache.

In such a case, the engine has no choice but to iterate over the entire array in exactly the right order, because anything else would observably break your program's behavior. In case of, the predicate function you pass might well care how often it gets called. Generally speaking, it's often impossible for engines to improve the complexity class of an operation. The time complexity of is O(n) (with n being the array's length), and it's fair to assume that it will remain that way.

Javascript array find