Chapter 7. Arrays
This chapter documents arrays, a fundamental datatype in JavaScript
and in most other programming languages.
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. JavaScript arrays may be sparse: the elements need not have
contiguous indexes, and there may be gaps. Every JavaScript array has a length
property. For nonsparse arrays, this property specifies the number of elements
in the array. For sparse arrays, length
is larger than the highest
index of any element.
JavaScript arrays are a specialized form of JavaScript object, and array indexes are really little more than property names that happen to be integers. We’ll talk more about the specializations of arrays elsewhere in this chapter. Implementations ...
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