Specification

The ECMAScript® Language Specification (a living standard) details everything about the JavaScript language, so anyone can implement their own JavaScript engine.

The following chapters need to be studied for our parser:

• Chapter 5: Notational Conventions
• Chapter 11: ECMAScript Language: Source Text
• Chapter 12: ECMAScript Language: Lexical Grammar
• Chapter 13 - 16: Expressions, Statements, Functions, Classes, Scripts and Modules
• Annex B: Additional ECMAScript Features for Web Browsers
• Annex C: The Strict Mode of ECMAScript

For navigation inside the specification:

• Anything clickable has a permanent link, they are shown on the URL as anchors, for example #sec-identifiers
• Hovering over things may show a tooltip, clicking on References shows all its references

Notational Conventions

Chapter 5.1.5 Grammar Notation is the section we need to read.

The things to note here are:

Recursion

This is how lists are presented in the grammar.

ArgumentList :
  AssignmentExpression
  ArgumentList , AssignmentExpression
``````javascript
a, b = 1, c = 2
^_____________^ ArgumentList
   ^__________^ ArgumentList, AssignmentExpression,
          ^___^ AssignmentExpression

VariableDeclaration : BindingIdentifier Initializer_opt

var binding_identifier;
var binding_identifier = Initializer;
                       ______________ Initializer_opt

ScriptBody : StatementList[~Yield, ~Await, ~Return]

ModuleItem :
  ImportDeclaration
  ExportDeclaration
  StatementListItem[~Yield, +Await, ~Return]
```<script src="javascript.js"></script><script type="module" src="main.mjs"></script>