Array in Javascript

JavaScript is probably the most forgiving language in existence when thought of in terms of data types and their conversions from one data type to another. The JavaScript engine does everything for you. In languages like the many flavors of C, you have to explicitly change the type of data with a statement before it can be used with another data type. This makes for a very tedious job when working with more than one data type, needlessly adding complexity.

JavaScript allows a variable to hold any data type at any time. A situation where this might be useful is when processing user information - the user inputs a string of numbers and you use this input to calculate something-or-other. You would of course use numbers in your calculation. JavaScript will automatically change the data type from the string type the user has input from the web page form to the Number data type so it can be used as part of the calculation. You'll run into many instances where the data type will be changed on the fly according to circumstances. The change of data type, if applicable, is given for each object, method, array, and property within the JavaScript Language Reference.

JavaScript Arrays

An Array is used to hold a piece or many pieces of information. In JavaScript, an array can hold one data type or all types - JavaScript just doesn't care. In languages such as the C flavors, an array can hold only one data type, which can cause headaches in implementation.

The items of an array are numbered starting from the number 0 (zero) and up. There is really no limit on the size of an array. This numbering system is called a Zero Based Index, and will be referred to as such in the coming discussions. The arrays you'll be working with to start with will be of the "shallow" type of array. That is, the array is only one level deep. An array can have an array existing within it - two arrays represented by one name. This type of array is called a MultiDimensional Array, and is considered to be a deep array. An array within JavaScript can be as deep as you have a need for, with the limit being about four levels deep (though I've personally played around with arrays up to twelve levels deep, just for fun). This restriction isn't due to the capabilities of JavaScript, but of the user's computer - you have no idea what the capabilities of the user's machine will be. Working with a very deep array may overwhelm the user's processor. There's a lot of math involved in accessing and working with arrays, though you don't see any of it - it is within the computer's processor and memory.

In the beginning versions of the JavaScript language, there wasn't a real array object to use - the closest was a string of objects with several properties associated with them. In the version 1.1 and up, there is a real array item that works as an array should. Creating your array and working with it is almost as simple as creating and working with variables - it is a simple statement that is easy to understand.