An array is an ordered collection of values. Each value is called an element, and each element has a numeric position in the array, known as its index. JavaScript arrays are untyped: an array element may be of any type, and different elements of the same array may be of different types. Array elements may even be objects or other arrays, which allows you to create complex data structures, such as arrays of objects and arrays of arrays. JavaScript arrays are zero-based and use 32-bit indexes: the index of the first element is 0, and the highest possible index is 4294967294 (2³²−2), for a maximum array size of 4,294,967,295 elements. JavaScript arrays are dynamic: they grow or shrink as needed and there is no need to declare a fixed size for the array when you create it or to reallocate it when the size changes. Every JavaScript array has a length property that specifies the number of elements in the array.