<ul><li>Elements in JavaScript arrays refer to the values stored at the array's indices, while internal data refers to hidden engine-level structures and optimizations used to manage arrays.</li><li>JavaScript's array methods like map() or forEach() do not rely on internal optimizations and work based on length and indexed properties, making them generic and usable on array-like objects.</li><li>Dense arrays have values at every index, while sparse arrays have 'holes' or indexes with no assigned value. JavaScript engines handle dense and sparse arrays differently in terms of optimization.</li><li>JavaScript engines track how arrays are used and assign internal 'kinds' that affect performance. The storage model for array elements depends on the array's usage and determines the performance of operations.</li></ul>

Understanding JavaScript Arrays: Internal Data vs Elements, and What Really Happens Under the Hood

Discover more