This chapter documents arrays, a fundamental datatype in JavaScript and in most other programming languages. An array is an ordered collection of values. Each value is called an element, and each element has a numeric position in the array, known as its index. JavaScript arrays are untyped: an array element may be of any type, and different elements of the same array may be of different types. Array elements may

This chapter covers JavaScript functions. Functions are a fundamental building block for JavaScript programs and a common feature in almost all programming languages. You may already be familiar with the concept of a function under a name such as subroutine or procedure. 本章介绍了 JavaScript 函数。函数是 JavaScript 程序的基本构建块，也是几乎所有

JavaScript objects were covered in Chapter 6. That chapter treated each object as a unique set of properties, different from every other object. It is often useful, however, to define a class of objects that share certain properties. Members, or instances, of the class have their own properties to hold or define their state, but they also have methods that define their behavior. These methods are defined by the class

The goal of modular programming is to allow large programs to be assembled using modules of code from disparate authors and sources and for all of that code to run correctly even in the presence of code that the various module authors did not anticipate. As a practical matter, modularity is mostly about encapsulating or hiding private implementation details and keeping the global namespace tidy so that modules cannot accidentally

Some datatypes, such as numbers and strings (Chapter 3), objects (Chapter 6), and arrays (Chapter 7) are so fundamental to JavaScript that we can consider them to be part of the language itself. This chapter covers other important but less fundamental APIs that can be thought of as defining the “standard library” for JavaScript: these

Iterable objects and their associated iterators are a feature of ES6 that we’ve seen several times throughout this book. Arrays (including TypedArrays) are iterable, as are strings and Set and Map objects. This means that the contents of these data structures can be iterated—looped over—wit