es5

ECMAScript 5 (ES5) is the fifth edition of the ECMAScript language specification, published in 2009 by ECMA International as ECMA-262, edition 5. It standardizes core language features and runtime behaviors to improve portability, reliability, and interoperability of JavaScript code across platforms and browsers.

Key features include strict mode, which enables a subset of the language with safer semantics by using the "use strict" directive. Strict mode changes error handling, disallows certain unsafe patterns, and helps catch common mistakes during development. ES5 also enhances object property definitions through getters and setters and the use of property descriptors with Object.defineProperty and Object.defineProperties. This allows fine-grained control over property attributes such as configurable, enumerable, and writable, and enables non-enumerable and read-only properties.

The language also introduces a standard JSON object with methods JSON.parse and JSON.stringify, improving the parsing and serialization of JSON data. Array handling was expanded with a library of methods, including forEach, map, filter, reduce, reduceRight, every, and some, along with Array.isArray. Function.prototype.bind provides partial application and explicit binding of this.

Additional object utilities include Object.create, Object.getPrototypeOf, Object.keys, Object.getOwnPropertyDescriptor, Object.getOwnPropertyNames, Object.freeze, Object.seal, and Object.preventExtensions, which together support more robust object modeling and immutability patterns.

Impact and legacy: ES5 was widely implemented across major browsers within a few years, enabling safer client-side development, improved JSON support, and better compatibility with evolving JavaScript patterns. It laid groundwork for subsequent editions and features later standardized in later ECMA revisions.