Get Assigned Identifiers

1.2.0 · maintenance · verified Sun Apr 19

The `get-assigned-identifiers` package provides a focused utility for JavaScript AST analysis, specifically designed to extract identifiers that are initialized by a given AST node, including those within destructuring assignments. It helps developers programmatically understand which variables are being declared or assigned in a specific scope, a common requirement for static analysis tools, code linters, and refactoring utilities. The current stable version is 1.2.0, which was published over six years ago, indicating a mature but infrequently updated library. Its primary differentiator is its single-purpose API, which allows for direct integration without the overhead of larger AST manipulation frameworks. While stable for its intended use cases, users should be aware of its age when integrating with very recent JavaScript syntax or modern AST parsers, as compatibility might not be actively maintained.

Common errors

```
TypeError: getAssignedIdentifiers is not a function
```
cause Attempting to use `getAssignedIdentifiers` before it's properly imported or if the imported value is `undefined`.

fix Ensure you are using the correct import statement for your module system: `const getAssignedIdentifiers = require('get-assigned-identifiers')` for CommonJS or `import getAssignedIdentifiers from 'get-assigned-identifiers'` for ESM.
```
SyntaxError: Cannot use import statement outside a module
```
cause Attempting to use ESM `import` syntax in a CommonJS context (e.g., a `.js` file without `"type": "module"` in `package.json` or run with `node --experimental-modules`).

fix Either use the CommonJS `require()` syntax (`const getAssignedIdentifiers = require('get-assigned-identifiers')`) or configure your project for ESM by adding `"type": "module"` to your `package.json` or saving the file as `.mjs`.

Warnings

gotcha The `get-assigned-identifiers` package has not been updated in over six years (last release v1.2.0). While its core functionality remains sound for older JavaScript syntax and AST specifications, it may not correctly parse or handle identifiers from very recent ECMAScript features (e.g., private class fields, new `import`/`export` syntax within modules) or be fully compatible with AST structures produced by modern parsers (e.g., Babel 7+, Acorn 8+).
Fix: Manually verify compatibility with your specific AST parser and JavaScript syntax target. Consider alternative, more actively maintained AST utility libraries for modern projects, or fork and update the package if critical for your use case.
gotcha The package expects an AST node from a parser like Acorn or Esprima. It does not provide its own parser. Ensure you are passing a valid AST node, typically an `Identifier` or `ObjectPattern`/`ArrayPattern` node.
Fix: Always use a robust JavaScript parser (e.g., `acorn`, `@babel/parser`, `esprima`) to generate the AST nodes before passing them to `getAssignedIdentifiers`.

Install

npm install get-assigned-identifiers npm
yarn add get-assigned-identifiers yarn
pnpm add get-assigned-identifiers pnpm

Imports

getAssignedIdentifiers
wrong:
```
import { getAssignedIdentifiers } from 'get-assigned-identifiers'
```
correct:
```
import getAssignedIdentifiers from 'get-assigned-identifiers'
```
The package uses a CommonJS default export, which translates to a default import in ESM. Avoid named imports.
getAssignedIdentifiers
```
const getAssignedIdentifiers = require('get-assigned-identifiers')
```
This is the documented and primary way to use the library in CommonJS environments.

Quickstart

Demonstrates how to parse JavaScript code using Acorn and then extract assigned identifiers from various AST node types, including object and array destructuring, and simple variable declarations.

import { parse } from 'acorn';
import getAssignedIdentifiers from 'get-assigned-identifiers';

const code = `
  const { a, b: [ c,, ...x ], d = 10 } = someComplexObject();
  let [ e, f ] = otherArray;
  var g = 'hello';
`;

try {
  const ast = parse(code, { ecmaVersion: 2020 });
  
  // Example 1: Destructuring declaration
  const node1 = ast.body[0].declarations[0].id; // { a, b: [ c,, ...x ], d = 10 }
  console.log('Identifiers from destructuring:', getAssignedIdentifiers(node1));
  // Expected: [{ name: 'a' }, { name: 'c' }, { name: 'x' }, { name: 'd' }]

  // Example 2: Array destructuring
  const node2 = ast.body[1].declarations[0].id; // [ e, f ]
  console.log('Identifiers from array destructuring:', getAssignedIdentifiers(node2));
  // Expected: [{ name: 'e' }, { name: 'f' }]

  // Example 3: Simple variable declaration
  const node3 = ast.body[2].declarations[0].id; // g
  console.log('Identifiers from simple declaration:', getAssignedIdentifiers(node3));
  // Expected: [{ name: 'g' }]

} catch (error) {
  console.error('Error parsing code:', error.message);
}

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