ECMAScript 5 Strict Mode, JSON, and More
Previously I analyzed ECMAScript 5’s Object and Property system. This is a huge new aspect of the language and deserved its special consideration. There are a number of other new features and APIs that need attention, as well. The largest of which are Strict Mode and native JSON support. Strict Mode Strict Mode is a new feature in ECMAScript 5 that allows you to place a program, or a function, in a “strict” operating context. Since ECMAScript 5 is backwards-compatible with ECMAScript 3, all of the “features” that were in ECMAScript 3 that were “deprecated” are just disabled (or throw errors) in strict mode, instead. Strict mode helps out in a couple ways: It catches some common coding bloopers, throwing exceptions.It prevents, or throws errors, when relatively “unsafe” actions are taken (such as gaining access to the global object).It disables features that are confusing or poorly thought out. Most of the information about strict mode can be found in the ES5 specification [PDF] on page #235.