periscopic

Utility for analyzing scopes belonging to an ESTree-compliant AST.

API

``js
import { analyze } from 'periscopic';

const ast = acorn.parse(
const a = b;
console.log(a);
);

const { map, globals, scope } = analyze(ast);
`

* map is a WeakMap, where the keys are the nodes of your AST that create a scope
* globals is a Map of all the identifiers that are referenced without being declared anywhere in the program (in this case, b and console)
* scope is the top-level Scope belonging to the program

$3

Each Scope instance has the following properties:

* scope.block — true if the scope is created by a block statement (i.e. let, const and class are contained to it), false otherwise
* scope.parent — the parent scope object
* scope.declarations — a Map of all the variables declared in this scope, the node value referes to the declaration statement
* scope.initialised_declarations — a Set of all the variables declared and initialised in this scope
* scope.references — a Set of all the names referenced in this scope (or child scopes)

It also has two methods:

* scope.has(name) — returns true if name is declared in this scope or an ancestor scope
* scope.find_owner(name) — returns the scope object in which name is declared (or null if it is not declared)

$3

This package also exposes utilities for extracting the identifiers contained in a declaration or a function parameter:

`js
import { extract_identifiers, extract_names } from 'periscopic';

const ast = acorn.parse(
const { a, b: [c, d] = e } = opts;
);

const lhs = ast.body[0].declarations[0].id;

extract_identifiers(lhs);
/*
[
{ type: 'Identifier', name: 'a', start: 9, end: 10 },
{ type: 'Identifier', name: 'c', start: 16, end: 17 },
{ type: 'Identifier', name: 'd', start: 19, end: 20 }
]
*/

extract_names(lhs);
/*
['a', 'c', 'd']
*/
``

License

MIT