Identify and eliminate computations that are performed repeatedly when they could be executed once. This includes moving loop-invariant checks outside of loops and reducing callback overhead that creates unnecessary function declarations. Common patterns to optimize: - **Loop invariants**: Move conditions that don't depend on individual loop items outside the loop - **Repeated function calls**: Cache results of expensive operations that don't change - **Callback overhead**: Minimize complex function declarations that cause GC churn Example from file upload validation: ```javascript // Before: checking upload limit for every file filesArray.some(file => { // ... file-specific checks ... || (files.length + media.size + pending > maxMediaAttachments) // This doesn't depend on individual file! }) // After: check upload limit once before processing files if (files.length + media.size + pending > maxMediaAttachments) { // handle error return; } // Then process individual files without redundant check ``` This optimization reduces computational overhead and improves performance, especially in scenarios with loops, callbacks, or frequently called functions.