JavaScript Objects and Arrays – JavaScript

Book Description

Objectives :
At the end of this chapter you will be able to:

• Understand the basic features of JavaScript arrays;
• Understand the fundamental elements of JavaScript arrays;
• Write HTML files using JavaScript arrays;
• Explain the JavaScript object model;
• Use arrays as objects.

Introduction :

Most high level computer programming languages provide ways for groups of related data to be collected together and referred to by a single name. JavaScript offers objects and arrays for doing so. JavaScript arrays are rather different from arrays in many programming languages: all arrays are objects (as in many other languages), but they are also associative arrays. Also, all objects can also be used as if they, too, are arrays.

This chapteris organised into four sections. It introduces arrays and objects separately, then considers arrays as objects, then finally considers objects as (associative) arrays. Many important concepts are covered in this unit, although much of the object technology concepts have been introduced in earlier units.

When working with variables, an important distinction has to be made: is the variable contain the value of a primitive type, or does it contain a reference to a (non-primitive) collection of data. A thorough grounding in the concepts covered in this chapter is necessary to both be able to understand the sophisticated Javascipt scripts written to support complex websites, and to be able to begin developing JavaScript solutions yourself for real world problems. It is important to work through examples until you understand them; write your own programmes that use and test your learning. Programming is learnt through doing as much, or more so, than by reading.

中文：

书名：JavaScript Objects and Arrays – JavaScript

Objectives :
在本章结束时，您将能够：

• 了解Java脚本数组的基本功能；
• 了解JavaScript数组的基本元素；
• 使用Java脚本数组编写HTML文件；
• 解释Java脚本对象模型；
• 将数组用作对象。

引言：

大多数高级计算机编程语言提供了将相关数据组收集在一起并由单个名称引用的方法。JavaScript提供了这样做的对象和数组。JavaScript数组与许多编程语言中的数组有很大不同：所有数组都是对象(就像在许多其他语言中一样)，但它们也是关联数组。此外，所有对象也可以像数组一样使用。

本章分为四个部分。它分别引入数组和对象，然后将数组视为对象，最后将对象视为(关联)数组。本单元涵盖了许多重要的概念，尽管许多对象技术概念在较早的单元中介绍过。

在使用变量时，必须进行重要的区分：变量是包含基元类型的值，还是包含对(非基元)数据集合的引用。为了能够理解为支持复杂网站而编写的复杂的Javascipt脚本，并且能够开始自己为现实世界的问题开发Java解决方案，有必要对本章涵盖的概念进行全面的了解。重要的是通过举例直到你理解它们；编写你自己的程序来使用和测试你的学习。编程是通过实践学习的，或者更多地通过阅读来学习。