Use of Arrays in Web Development Programming JavaScript

The array creation functions organized into two categories: those that place the enhanced properties at the end, and those that put the enhanced features at the beginning.

The first four array creation methods place the improved properties at the end of the array and initialize all empty slots to "@." They differ in how they handle the improved properties.And the final three creation methods place the improved properties at the beginning of the array. This set of methods can be used to examine the consequences of not initializing the array, or initializing all of the elements to the same thing, and of initializing only the empty elements.

Associative Array

An associative array is a one-dimensional array of pairs. You access the left member of the pair with a numeric index. You access the right member of the pair with a string index equal to the value of the left member of the pair. For example, (left) myArray[1] = "red" but (right) myArray["red"]= "FF0000".

One of the biggest criticisms of associative arrays is that they are one dimensional. The argument made that the left and right sides constitute a second dimension, of size two, but this is not an actual multi-dimensional array.
In fact, two-dimensional arrays are really just arrays of arrays. Because of the nature of associative arrays, one can develop such complex structures with relative ease.

The function lotsOfColors() starts off by creating the associative array, colors, as well as a comma delimited string that lists the colors it uses. It then cycles through a loop for each color to be processed.
It first extracts the color we want from colorstring (as a string) and then sets the left element of the current associative pair to that string.

Arrays explicitly created by a function that takes a generic this object and gives it a size.
A Windows.ini file is an excellent example of the use of associative pairs. Every entry has a left element, such as *.doc, and a right element, such as c:winword.winword.exe.
In this case, the association is a relationship between a file suffix and the application that created it. Hypertext links are also associations, just ordered backward.

One array which arises frequently in JavaScript applications is an array of newly created child windows, since JavaScript does not provide such an array by default.
The function winArrayAdd( ) can be used to add a window to such a window array.
Since an array is just an unstructured object, we can conveniently make it into a more complex object. For example, we can add a description property to an array.
This is useful because the array may have a short name that is easy to use elsewhere in our code, but that name may not be very illustrative of the array's purpose.

An array is a primordial JavaScript object. Its properties, which represent the array members, can be anything. You must set the special property known as size, however, in your creation function. This property gives the length of the array (and is occasionally referred to as length for that reason). The size property usually put in the zeroth element of the array during initialization.

It means that your arrays will have n+1 elements in total; n elements for data, and one extra element at index zero to hold the array size. You need to be sure that your array access functions do not overwrite the zero elements.

The question is where in the element list they should be placed. If we put at the beginning, the array elements proper do not start at index=1. If we bring them at the end, the array elements are in the right place, but it is now harder to increase the size of the array.
It is because there are referencing problems if you access the properties by their array index, rather than by their names. We will examine the advantages and drawbacks of both approaches.

There is no initialization of the right members of the array. You can also arrange to do this in the createArray function, but only with some effort.

It is because the left element must be unique, and we have initialized all the array elements to the same value, namely the value init. If you have two array members containing the same value, you are only able to get to the first one.
In addition to creating arrays, it is often desirable to be able to reset or clear an array so that it may reuse. A particular procedure, known as a double replacement scheme, must be used to clear or reset an existing array.

This unique approach is needed because you have no way of knowing what values already stored in the array. In particular, you have no way of knowing that they are unique.



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