Clojure's core/assoc_in in TypeScript

How to use

Install via yarn add locutus and import: import { assoc_in } from 'locutus/clojure/core/assoc_in'.

Or with CommonJS: const { assoc_in } = require('locutus/clojure/core/assoc_in')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	assoc_in({a: {b: 1}}, ['a', 'b'], 2)	{a: {b: 2}}
2	assoc_in({a: {}}, ['a', 'c'], 10)	{a: {c: 10}}
3	assoc_in([1, {x: 3}], [1, 'x'], 9)	[1, {x: 9}]

Notes

• Immutably associates a value at a nested path, similar to Clojure assoc-in.

Here's what our current TypeScript equivalent to Clojure's core/assoc_in looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

type PathKey = string | number

function cloneForKey(value: unknown, nextKey?: PathKey): Record<string | number, unknown> | unknown[] {
  if (Array.isArray(value)) {
    return value.slice()
  }
  if (typeof value === 'object' && value !== null) {
    return { ...(value as Record<string | number, unknown>) }
  }
  return typeof nextKey === 'number' ? [] : {}
}

export function assoc_in(value: unknown, keys: PathKey[] | unknown, newValue: unknown): unknown {
  //  discuss at: https://locutus.io/clojure/assoc_in/
  // original by: Kevin van Zonneveld (https://kvz.io)
  //      note 1: Immutably associates a value at a nested path, similar to Clojure assoc-in.
  //   example 1: assoc_in({a: {b: 1}}, ['a', 'b'], 2)
  //   returns 1: {a: {b: 2}}
  //   example 2: assoc_in({a: {}}, ['a', 'c'], 10)
  //   returns 2: {a: {c: 10}}
  //   example 3: assoc_in([1, {x: 3}], [1, 'x'], 9)
  //   returns 3: [1, {x: 9}]

  if (!Array.isArray(keys)) {
    return value
  }

  if (keys.length === 0) {
    return newValue
  }

  const root = cloneForKey(value, keys[0])
  let sourceCursor: unknown = value
  let targetCursor: Record<string | number, unknown> | unknown[] = root

  for (let i = 0; i < keys.length - 1; i++) {
    const key = keys[i]
    const nextKey = keys[i + 1]
    if (key === undefined || nextKey === undefined) {
      continue
    }

    const sourceNext =
      sourceCursor !== null && typeof sourceCursor === 'object'
        ? (sourceCursor as Record<string | number, unknown>)[key]
        : undefined

    const clonedNext = cloneForKey(sourceNext, nextKey)
    ;(targetCursor as Record<string | number, unknown>)[key] = clonedNext

    sourceCursor = sourceNext
    targetCursor = clonedNext
  }

  const leafKey = keys[keys.length - 1]
  if (leafKey === undefined) {
    return root
  }

  ;(targetCursor as Record<string | number, unknown>)[leafKey] = newValue
  return root
}

function cloneForKey(value, nextKey) {
  if (Array.isArray(value)) {
    return value.slice()
  }
  if (typeof value === 'object' && value !== null) {
    return { ...value }
  }
  return typeof nextKey === 'number' ? [] : {}
}

export function assoc_in(value, keys, newValue) {
  //  discuss at: https://locutus.io/clojure/assoc_in/
  // original by: Kevin van Zonneveld (https://kvz.io)
  //      note 1: Immutably associates a value at a nested path, similar to Clojure assoc-in.
  //   example 1: assoc_in({a: {b: 1}}, ['a', 'b'], 2)
  //   returns 1: {a: {b: 2}}
  //   example 2: assoc_in({a: {}}, ['a', 'c'], 10)
  //   returns 2: {a: {c: 10}}
  //   example 3: assoc_in([1, {x: 3}], [1, 'x'], 9)
  //   returns 3: [1, {x: 9}]

  if (!Array.isArray(keys)) {
    return value
  }

  if (keys.length === 0) {
    return newValue
  }

  const root = cloneForKey(value, keys[0])
  let sourceCursor = value
  let targetCursor = root

  for (let i = 0; i < keys.length - 1; i++) {
    const key = keys[i]
    const nextKey = keys[i + 1]
    if (key === undefined || nextKey === undefined) {
      continue
    }

    const sourceNext = sourceCursor !== null && typeof sourceCursor === 'object' ? sourceCursor[key] : undefined

    const clonedNext = cloneForKey(sourceNext, nextKey)
    targetCursor[key] = clonedNext

    sourceCursor = sourceNext
    targetCursor = clonedNext
  }

  const leafKey = keys[keys.length - 1]
  if (leafKey === undefined) {
    return root
  }

  targetCursor[leafKey] = newValue
  return root
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

View on GitHub · Edit on GitHub · View Raw

---

We have 14 Clojure functions so far - help us add more

Got a rainy Sunday afternoon and a taste for a porting puzzle?

• Get inspiration from ClojureDocs.
• Click "New file" in the appropriate folder on GitHub. This will fork the project to your account, directly add the file to it, and send a Pull Request to us.

We will then review it. If it's useful to the project and in line with our contributing guidelines your work will become part of Locutus and you'll be automatically credited in the authors section accordingly.

« More Clojure core functions

Star