ast-walker-scope

Traverse Babel AST with scope information.

Inherited from estree-walker.

Install

1npm i ast-walker-scope

Usage

Basic Example

For a real example, you can refer to example.ts

1import { walk } from 'ast-walker-scope'
2
3const code = `
4const a = 'root level'
5
6{
7  const a = 'second level'
8  let secondLevel = true
9  console.log(a, secondLevel)
10}
11
12var err = undefined
13try {
14} catch (err) {
15  console.log(err)
16}
17
18console.log(a)
19`.trim()
20
21walk(code, {
22  leave(this, node) {
23    if (node.type === 'CallExpression') {
24      console.log(`\nLevel: ${this.level}`)
25      for (const [name, node] of Object.entries(this.scope)) {
26        console.log(
27          `variable ${name} is located at line ${node.loc?.start.line}, column ${node.loc?.start.column}`,
28        )
29      }
30    }
31  },
32})

Output:

Level: 2
variable a is located at line 4, column 8
variable secondLevel is located at line 5, column 6

Level: 2
variable a is located at line 1, column 6
variable err is located at line 12, column 9

Level: 1
variable a is located at line 1, column 6
variable err is located at line 9, column 4

Typings

1export type Scope = Record<string, Node>
2export interface HookContext extends WalkerContext {
3  // inherited from estree-walker
4  skip: () => void
5  remove: () => void
6  replace: (node: Node) => void
7
8  // arguments of estree-walker hook
9  parent: Node
10  key: string
11  index: number
12
13  // scope info
14  scope: Scope
15  scopes: Scope[]
16  level: number
17}

Sponsors

Credits

• @vue/reactivity-transform - almost copy-like referenced

License

MIT License © 2022-PRESENT 三咲智子