Mutateless

Mutateless is a small utility module which provide a bunch of functions for working with immutable data structures. Instead of polluting or changing the way you work with your objects, we designed the functions to work on regular objects, lists and nested data structures of any kind.

Installation

yarn add mutateless

Examples

Lets start by looking at assign, which acts almost like Object.assign:

const todo = {
  title: 'sleep', 
  checked: false,
  notes: ['Go to bed before midnight']
}

const modifiers = {
  checked: true,
  notes: notes => [...notes, 'another note']
}

assign(modifiers, todo) // => new object with with a second note

We first pass in the properties we want to modify, each property can either be a value or a modifier function. The modifier function will receive the original value and should return the new value. You will soon see why we received the original value but first lets take a look at another function called add:

add(4, [1,2,3]) // => [1,2,3,4]

add will return a new list with the appended value. But add is also a curried function, if we only pass in the first parameter we will receive a new function which accepts the second parameter. Lets combine assign and the curried add:

assign({notes: add('another note')}, todo) // => new object with with a second note

Which is equivalent to:

assign({notes: notes => add('another note', notes)}, todo) // => new object with with a second note

remove can be used to remove items matching a reference or a predicate:

assign({notes: remove('another note')}, todo) // => new object with without the second note

modifying a nested object works the same way:

const article = {
  // ...
  author: {
    // ...
    username: 'jack.bauer'
  }
}

const setUsername = username => assign({username}) // => curried assign which accepts an object/list

assign({author: setUsername('kiefer.sutherland')}, article) // => new article with updated author.username

mutateless contains a some generic and useful predicates to help you write more readable and predictable code.

Lets take a look at the match predicate:

const todos = [
    {title: 'Bake cake', checked: true},
    {title: 'Eat cake', checked: false},
    {title: 'Profit', checked: false},   
]

const unchecked = match({checked: false}) 

replace(unchecked, assign({checked: true}), todos) // => check all elements

and the here is last predicate:

remove(last, todos) // => new list without the last item

For more examples read the tests or the documentation

License

MIT