Javascript Arrays

An Array is an object which stores multiple values and has various properties. When you declare an array, you must declare the name of it, and then how many values it will need to store. It is important to realize that each value is stored in one of the elements of the array, and these elements start at 0. This means that the first value in the array is really in the 0 element, and the second number is really in the first element. So for example, if I want to store 10 values in my array, the storage elements would range from 0-9.

The notation for declaring an array looks like this:

myArray = new Array(10); foo = new Array(5);

Initially, all values are set to null. The notation for assigning values to each unit within the array looks like this:

myArray[0] = 56; 
myArray[1] = 23; 
myArray[9] = 44;

By putting the element number in brackets [ ] after the array's name, you can assign a value to that specific element. Note that there is no such element, in this example, as myArray[10]. Remember, the elements begin at myArray[0] and go up to myArray[9].

In JavaScript, however, an array's length increases if you assign a value to an element higher than the current length of the array. The following code creates an array of length zero, then assigns a value to element 99. This changes the length of the array to 100.

colors = new Array(); 
colors[99] = "midnightblue";

Be careful to reference the right cells, and make sure to reference them properly!

Because arrays are objects, they have certain properties that are pre-defined for your convenience. For example, you can find out how many elements myArray has and store this value in a variable called numberOfElements by using:

numberOfElements = myArray.length;