https://hacks.mozilla.org/2015/04/es6-in-depth-an-introduction/

What falls under the scope of ECMAScript?

The JavaScript programming language is standardized by ECMA (a standards body like W3C) under the name ECMAScript. Among other things, ECMAScript defines:

• Language syntax – parsing rules, keywords, statements, declarations, operators, etc.
• Types – boolean, number, string, object, etc.
• Prototypes and inheritance
• The standard library of built-in objects and functions – JSON, Math, Array methods, Object introspection methods, etc.

What it doesn’t define is anything to do with HTML or CSS, or the Web APIs, such as the DOM (Document Object Model). Those are defined in separate standards. ECMAScript covers the aspects of JS that are present not only in the browser, but also in non-browser environments such as node.js.

ECMAScript Web APIs node.js