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simple scope analysis for javascript ASTs. tracks scopes and collects references to variables.

Caveats and/or todos:

  • This code is extracted from browser-pack-flat—currently browser-pack-flat's test suite are the only tests for this module.
  • May be missing edge cases. Things like label:s are not considered at all, but ideally in the future they will!

stability npm travis standard


npm install scope-analyzer


Note: AST nodes passed to scope-analyzer functions are expected to reference the parent node on a node.parent property. Nodes from falafel or transform-ast have a .parent property, but others may not, so make sure you've got that set up somehow.

var scan = require('scope-analyzer')
var ast = parse('...')
// Initialize node module variables
scan.createScope(ast, ['module', 'exports', '__dirname', '__filename'])
var binding = scan.getBinding(ast, 'exports')
binding.getReferences().forEach(function (reference) {
  // Assume for the sake of the example that all references to `exports` are assignments like
  // ` = abc`
  console.log('found export:',



Walk the ast and analyze all scopes. This will immediately allow you to use the get* methods on any node in the tree.


Visit a node to check if it initialises any scopes. For example, a function declaration will initialise a new scope to hold bindings for its parameters. Use this if you are already walking the AST manually, and if you don't need the scope information during this walk.


Visit a node to check if it is a reference to an existing binding. If it is, the reference is added to the parent scope. Use this if you are already walking the AST manually.

createScope(node, bindings)

Initialise a new scope at the given node. bindings is an array of variable names. This can be useful to make the scope analyzer aware of preexisting global variables. In that case, call createScope on the root node with the names of globals:

var ast = parse('xyz')
scopeAnalyzer.createScope(ast, ['HTMLElement', 'Notification', ...])


Get the Scope initialised by the given node.

getBinding(node, name)

Get the Binding named name that is available to node. The binding must be declared in the current scope or a scope initialised by any parent node.



Check if this scope defines name.


Get the Binding named name that is declared by this scope.


Get a list of all nodes referencing the name binding that is declared by this scope.

scope.forEach(cb(binding, name))

Loop over all bindings declared by this scope.



The node that defined this binding.


Return an array of nodes that reference this binding.