update-set

update-set is a path-based setter for building update payloads.

Unlike lodash.set, it does not write the raw value to the leaf node. It always stores:

{ __set__: true, __value__: value }

This makes it possible to distinguish "this field was explicitly updated" from ordinary object data.

Install

npm install update-set

Usage

import set from 'update-set';

const target = {};

set(target, 'profile.name', 'Neo');

console.log(target);
// {
//   profile: {
//     name: {
//       __set__: true,
//       __value__: 'Neo'
//     }
//   }
// }

Path semantics

update-set treats dot paths and bracket index paths differently:

import set from 'update-set';

const objectPath = {};
set(objectPath, 'a.2.c', 'value');
// {
//   a: {
//     2: {
//       c: {
//         __set__: true,
//         __value__: 'value'
//       }
//     }
//   }
// }

const arrayPath = {};
set(arrayPath, 'a[2].c', 'value');
// {
//   a: [
//     undefined,
//     undefined,
//     {
//       c: {
//         __set__: true,
//         __value__: 'value'
//       }
//     }
//   ]
// }

• a.2.c treats 2 as an object key.
• a[2].c treats 2 as an array index.
• Array-form paths are supported: set(target, ['items', 1, 'name'], 'Neo').

Nested updates on wrapped values

If a node has already been wrapped with __set__ and __value__, later nested updates continue inside __value__:

import set from 'update-set';

const target = {};

set(target, 'config', { enabled: false, name: 'demo' });
set(target, 'config.enabled', true);

console.log(target);
// {
//   config: {
//     __set__: true,
//     __value__: {
//       enabled: {
//         __set__: true,
//         __value__: true
//       },
//       name: 'demo'
//     }
//   }
// }

Notes

• set(null, path, value) returns null and does nothing.
• Quoted numeric bracket indices such as list["1"].done still work, but they log a deprecation warning. Prefer list[1].done.

API

declare function set<T extends object>(
  object: T,
  path: string | number | ReadonlyArray<string | number>,
  value: any,
): T;