Array vs. Linked List: Key Differences, Performance & When to Use
An Array is a contiguous block of memory that stores elements side-by-side with fixed indexing; a Linked List is a chain of nodes, each holding data plus a pointer to the next, allowing scattered memory locations.
People picture both as “lists,” so they assume appending is always cheap. In reality, deleting the first element of an Array shifts everything, while Linked Lists make that instant—yet random access crawls. This mismatch trips up new coders in interviews and production debugging alike.
Key Differences
Arrays give O(1) random access and cache-friendly locality; Linked Lists offer O(1) insert/delete anywhere at the cost of extra memory per pointer and slower cache performance. Arrays have fixed size unless resized (O(n)); Linked Lists grow flexibly but lack true random indexing.
Which One Should You Choose?
Pick Array when you need fast reads and know the count up-front—think pixel buffers or lookup tables. Pick Linked List when insertions/deletions dominate—like LRU caches, music playlists, or frequent undo stacks. Hybrid structures (e.g., ArrayList, unrolled lists) often balance both.
Can I mix the two?
Yes—use an ArrayList for storage and add next pointers to create a “skip list,” gaining cache speed plus flexible inserts.
Does JavaScript use Arrays or Linked Lists?
JavaScript arrays are dynamic, resizable contiguous buffers with methods like push/pop; under the hood they behave like ArrayLists, not classic Linked Lists.
When does cache locality really matter?
In high-frequency loops—gaming engines, numeric simulations—missing the CPU cache can slow you 5-10×, making Arrays the clear winner.