ECMAScript is the formal standard that defines the JavaScript programming language. It is published by Ecma International as the standard ECMA-262. Because the web relies on many independent browsers running the same scripts, JavaScript needed a single specification that every implementation could follow. Standardization began in 1996 under Ecma International, and the work was carried out by its technical committee TC39.
The first edition of ECMA-262 was published in June 1997. The standard uses the name “ECMAScript” rather than “JavaScript” because, as the history “JavaScript: The First 20 Years” explains, the word “JavaScript” was a trademark and was avoided in the specification. In practice “JavaScript” and “ECMAScript” are different names for essentially the same language.
The standard has been revised many times. A second edition followed in 1998 and a third in 1999. A planned fourth edition was abandoned and never published. Work resumed with the fifth edition in 2009, and the sixth edition, known as ECMAScript 2015, introduced a large set of new features that became the foundation for the language’s modern evolution.
Since 2015, TC39 has shifted to a yearly release schedule, publishing a new edition of the standard each June. This regular cadence keeps the official definition of JavaScript current with the features that browsers and other implementations ship.