Array Summary
JavaScript array creation, usage, and compatibility techniques can be confusing. Here are the main points of this chapter in review:
- Arrays and objects are the same thing in JavaScript. Any object can have array elements, and any array can have object properties.
- In Navigator 3.0, there are three methods that can be used to manipulate arrays:
- You can can convert an array, and all of its elements into a single string with the
Array.join()method. - You can reverse the order of elements in an array with the
Array.reverse()method. - You can sort the elements of an array with the
Array.sort()method.
- You can can convert an array, and all of its elements into a single string with the
- In Navigator 3.0 and Internet Explorer 3.0, array elements and object properties do not overlap and cannot overwrite each other. There is an
Array()constructor, and arrays created with this constructor have a (read-only in IE 3.0)lengthproperty that is automatically maintained so that it always contains a value one greater than the largest index of the array. - In Navigator 2.0, object properties and array elements overlap; when you create a new property, it is as if you added a new array element one higher than the highest existing element. There is no built-in
Array()constructor, but you can write your own. Also, there is no automatically maintainedlengthproperty, but it is common to reserve element 0 of an array for asizeproperty (which you update yourself as the array grows). - For many algorithms, the size of an array is maintained in a variable externally to an array, and there is no need for a
lengthorsizeproperty. - All arrays in JavaScript are implemented as associative arrays, and can be "sparse"--i.e., they can contain non-contiguous elements. Usually, though, you'll use arrays as if they were non-associative, fixed-size arrays like those found in C, C++, and Java.