Simple-update-in NPM

simple-update-in

A lightweight updateIn for immutable objects.

We love ImmutableJS. But sometimes, we want to start something from small. Thus, we created this package with zero dependencies.

Under the cover, we use Rest Operator to do most of the heavylifting.

Install

For latest stable, run npm install simple-update-in.

For active development (master branch), run npm install simple-update-in@master.

How to use

We share similar signature as ImmutableJS.updateIn:

updateIn(
  target: Array|Map,
  path: (Number|String)[],
  updater?: (value: any) => any
)

To make updateIn efficient, especially, when paired with React. It will return a mixed deep/shallow clone of the target. It only deep clone on objects that it modified along the path, and shallow clone objects that it did not modify.

Example

Just like ImmutableJS, we want to make both Array and Map a first-class citizen. To work on a map, use a string as key. For arrays, use a number as key.

Map

import updateIn from 'simple-update-in';

const from = { one: 1, two: { number: 2 }, thirty: 3 };
const actual = updateIn(from, ['thirty'], three => three * 10);

expect(actual).toEqual({ one: 1, two: { number: 2 }, thirty: 30 });

expect(actual).not.toBe(from);   // Something under this tree has changed
expect(actual.two).toBe(to.two); // Nothing under this tree has changed
expect(actual.thirty).toBe(30);  // We multiplied it by 10

This is in fact an "upsert" operation.

Array in map

const from = { one: [1.1, 1.2, 1.3], two: [2] };
const actual = updateIn(from, ['one', 1], value => 'one point two');

expect(actual).toEqual({ one: [1.1, 'one point two', 1.3], two: [2] });

Remove a key

You can also use updateIn to remove a key by passing a falsy value to the updater argument.

const from = { one: 1, two: 2 };
const actual = updateIn(from, ['two']);

expect(actual).toEqual({ one: 1 });

expect(actual).not.toBe(from);
expect(actual).not.toHaveProperty('two');

Remove an item in array

const from = ['zero', 'one', 'two'];
const actual = updateIn(from, [1]);

expect(actual).toEqual(['zero', 'two']);

Automatic expansion

const from = {};
const actual = updateIn(from, ['one', 'two'], 1.2);

expect(actual).toEqual({ one: { two: 1.2 } });

Replace incompatible types

If incompatible types is found along the walk, they will be replaced. For example, in the following example, an Array is replaced by a Map.

const from = [0, 1, 2];
const actual = updateIn(from, ['one'], 1);

expect(actual).toEqual({ one: 1 });

In the path, 'one' is a string, it implies that user want a Map instead of Array

It will also replace number with Map.

const from = { one: 1 };
const actual = updateIn(from, ['one', 'two'], 1.2);

expect(actual).toEqual({ one: { two: 1.2 } });

Adding an item to array

You can use special index value -1 to indicate an append to the array.

const from = [0, 1];
const actual = updateIn(from, [-1], 2);

expect(actual).toEqual([0, 1, 2]);

There is no support on prepend or insertion, however, you can use Rest Operator for array manipulation.

const from = { numbers: ['one', 'two'] };
const actual = updateIn(from, ['numbers'], array => ['zero', ...array]);

expect(actual).toEqual({ numbers: ['zero', 'one', 'two'] });