JavaScript: The Good Parts

Analyzing JavaScript

JavaScript is built on some very good ideas and a few very bad ones.

The very good ideas include functions, loose typing, dynamic objects, and an expressive object literal notation. The bad ideas include a programming model based on global variables.

JavaScript's functions are first class objects with (mostly) lexical scoping. JavaScript is the first lambda language to go mainstream. Deep down, JavaScript has more in common with Lisp and Scheme than with Java. It is Lisp in C's clothing. This makes JavaScript a remarkably powerful language.

The fashion in most programming languages today demands strong typing. The theory is that strong typing allows a compiler to detect a large class of errors at compile time. The sooner we can detect and repair errors, the less they cost us. JavaScript is a loosely typed language, so JavaScript compilers are unable to detect type errors. This can be alarming to people who are coming to JavaScript from strongly typed languages. But it turns out that strong typing does not eliminate the need for careful testing. And I have found in my work that the sorts of errors that strong type checking finds are not the errors I worry about. On the other hand, I find loose typing to be liberating. I don't need to form complex class hierarchies. And I never have to cast or wrestle with the type system to get the behavior that I want.

JavaScript has a very powerful object literal notation. Objects can be created simply by listing their components. ...