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+# Acorn AST walker
+
+An abstract syntax tree walker for the
+[ESTree](https://github.com/estree/estree) format.
+
+## Community
+
+Acorn is open source software released under an
+[MIT license](https://github.com/acornjs/acorn/blob/master/LICENSE).
+
+You are welcome to
+[report bugs](https://github.com/acornjs/acorn/issues) or create pull
+requests on [github](https://github.com/acornjs/acorn). For questions
+and discussion, please use the
+[Tern discussion forum](https://discuss.ternjs.net).
+
+## Installation
+
+The easiest way to install acorn is from [`npm`](https://www.npmjs.com/):
+
+```sh
+npm install acorn-walk
+```
+
+Alternately, you can download the source and build acorn yourself:
+
+```sh
+git clone https://github.com/acornjs/acorn.git
+cd acorn
+npm install
+```
+
+## Interface
+
+An algorithm for recursing through a syntax tree is stored as an
+object, with a property for each tree node type holding a function
+that will recurse through such a node. There are several ways to run
+such a walker.
+
+**simple**`(node, visitors, base, state)` does a 'simple' walk over a
+tree. `node` should be the AST node to walk, and `visitors` an object
+with properties whose names correspond to node types in the [ESTree
+spec](https://github.com/estree/estree). The properties should contain
+functions that will be called with the node object and, if applicable
+the state at that point. The last two arguments are optional. `base`
+is a walker algorithm, and `state` is a start state. The default
+walker will simply visit all statements and expressions and not
+produce a meaningful state. (An example of a use of state is to track
+scope at each point in the tree.)
+
+```js
+const acorn = require("acorn")
+const walk = require("acorn-walk")
+
+walk.simple(acorn.parse("let x = 10"), {
+  Literal(node) {
+    console.log(`Found a literal: ${node.value}`)
+  }
+})
+```
+
+**ancestor**`(node, visitors, base, state)` does a 'simple' walk over
+a tree, building up an array of ancestor nodes (including the current node)
+and passing the array to the callbacks as a third parameter.
+
+```js
+const acorn = require("acorn")
+const walk = require("acorn-walk")
+
+walk.ancestor(acorn.parse("foo('hi')"), {
+  Literal(_, ancestors) {
+    console.log("This literal's ancestors are:", ancestors.map(n => n.type))
+  }
+})
+```
+
+**recursive**`(node, state, functions, base)` does a 'recursive'
+walk, where the walker functions are responsible for continuing the
+walk on the child nodes of their target node. `state` is the start
+state, and `functions` should contain an object that maps node types
+to walker functions. Such functions are called with `(node, state, c)`
+arguments, and can cause the walk to continue on a sub-node by calling
+the `c` argument on it with `(node, state)` arguments. The optional
+`base` argument provides the fallback walker functions for node types
+that aren't handled in the `functions` object. If not given, the
+default walkers will be used.
+
+**make**`(functions, base)` builds a new walker object by using the
+walker functions in `functions` and filling in the missing ones by
+taking defaults from `base`.
+
+**full**`(node, callback, base, state)` does a 'full' walk over a
+tree, calling the callback with the arguments (node, state, type) for
+each node
+
+**fullAncestor**`(node, callback, base, state)` does a 'full' walk
+over a tree, building up an array of ancestor nodes (including the
+current node) and passing the array to the callbacks as a third
+parameter.
+
+```js
+const acorn = require("acorn")
+const walk = require("acorn-walk")
+
+walk.full(acorn.parse("1 + 1"), node => {
+  console.log(`There's a ${node.type} node at ${node.ch}`)
+})
+```
+
+**findNodeAt**`(node, start, end, test, base, state)` tries to locate
+a node in a tree at the given start and/or end offsets, which
+satisfies the predicate `test`. `start` and `end` can be either `null`
+(as wildcard) or a number. `test` may be a string (indicating a node
+type) or a function that takes `(nodeType, node)` arguments and
+returns a boolean indicating whether this node is interesting. `base`
+and `state` are optional, and can be used to specify a custom walker.
+Nodes are tested from inner to outer, so if two nodes match the
+boundaries, the inner one will be preferred.
+
+**findNodeAround**`(node, pos, test, base, state)` is a lot like
+`findNodeAt`, but will match any node that exists 'around' (spanning)
+the given position.
+
+**findNodeAfter**`(node, pos, test, base, state)` is similar to
+`findNodeAround`, but will match all nodes *after* the given position
+(testing outer nodes before inner nodes).