immutable-ops

A collection of functions to perform immutable operations on plain JavaScript objects and arrays.

Like updeep but with batched mutations and no freezing.

Like icepick, but with batched mutations and a curried API that puts the target object as the last argument. No freezing.

Features

• Small. It's just 10 functions.
• Functional API with curried functions
• JavaScript in, JavaScript out
• Batched mutations

Installation

npm install immutable-ops

Example Usage

import compose from 'ramda/src/compose';
import ops from 'immutable-ops';

// These are all the available functions.
const {
    // Functions operating on objects.
    merge,
    mergeDeep,
    omit,
    setIn,

    // Functions operating on arrays.
    insert,
    splice,
    push,
    filter,

    // Functions operating on both
    set,

    // Placeholder for currying.
    __,
} = ops;

const arr = [1, 2, 3];

const pushFour = ops.push(4);
const pushFive = ops.push(5);

// All functions are curried. These functions
// still need the final argument, the array to
// operate on.
expect(pushFive).to.be.a('function');

const pushFourAndFive = compose(pushFive, pushFour);

const result = pushFourAndFive(arr);
// Two new arrays were created during `pushFourAndFive` execution.
expect(result).to.deep.equal([1, 2, 3, 4, 5]);



// Only one new array is created.
const sameResult = ops.batched(batchedOps => {
    // batchedOps is able to keep track of mutated
    // objects.
    return compose(
        batchedOps.push(5),
        batchedOps.push(4)
    )(arr);
});

expect(sameResult).to.deep.equal([1, 2, 3, 4, 5]);

Batched Mutations

A batch token is supplied by the user at the start of a batch, or created by immutable-ops. Each newly created object within a batch is tagged with that token. If a batch using token X operates on an object that is tagged with token X, it is free to mutate it. You can think of it as an ownership; the batch owns the newly created object and therefore is free to mutate it. New batches use a token Y that will never be equal to the previous token.

Tags are not removed; They are assigned to a non-enumerable property @@_______immutableOpsOwnerID which should avoid any collisions.

This token strategy is similar to what ImmutableJS uses to track batches.

Manually using batch tokens

ops.batch gives you access to all the immutable-ops functions that take a token as their additional first argument. Otherwise they are identical to the functions found in ops directly.

import ops from 'immutable-ops';
const token = ops.getBatchToken();

// This object has no batch token, since it was not created by immutable-ops.
const obj = {a: 1, b: 2};

// obj2 is a newly created object tagged with the token.
const obj2 = ops.batch.set(token, 'a', 10, obj);
expect(obj).to.not.equal(obj2)

// Because we operate on obj2 that has the same token as
// we passed to the function, obj2 is mutated.
const obj3 = ops.batch.set(token, 'b', 20, obj2);
expect(obj2).to.equal(obj3);

Handling batch tokens implicitly

import ops from 'immutable-ops';

const obj = {a: 1, b: 2};

const obj3 = ops.batched(batchedOps => {
    // batchedOps has functions that are bound to a new batch token.
    const obj2 = batchedOps.set('a', 10, obj);
    return batchedOps.set('b', 20, obj2);
});

Currying

All operations are curried by default. Functions are curried with ramda.curry. In addition to normal currying behaviour, you can use the ramda placeholder variable available in ops.__ to specify parameters you want to pass arguments for later. Example:

const removeNFromHead = ops.splice(/* startIndex */ 0, /* deleteCount */ops.__, /* valsToAdd */[]);
const removeTwoFromHead = removeNFromHead(2);
const arr = [1, 2, 3];

console.log(removeTwoFromHead(arr));
// [3];

Object API

merge(mergeObj, targetObj)

Performs a shallow merge on targetObj. mergeObj can be a single object to merge, or a list of objects. If a list is passed as mergeObj, objects to the right in the list will have priority when determining final attributes.

Returns the merged object, which will be a different object if an actual change was detected during the merge.

const result = ops.merge(
    // mergeObj
    {
        a: 'theA',
        b: {
            c: 'nestedC',
        },
    },
    // targetObj
    {
        a: 'theA2',
        b: {
            d: 'nestedD',
        },
        c: 'theC',
    }
);

console.log(result);
// {
//     {
//         a: 'theA',
//         b: {
//             c: 'nestedC'
//         },
//         c: 'theC',
//     },
// }

deepMerge(mergeObj, targetObj)

Same as merge, but performs merge recursively on attributes that are objects (not arrays).

const result = ops.deepMerge(
    // mergeObj
    {
        a: 'theA',
        b: {
            c: 'nestedC',
        },
    },
    // targetObj
    {
        a: 'theA2',
        b: {
            d: 'nestedD',
        },
        c: 'theC',
    }
);

console.log(result);
// {
//     {
//         a: 'theA',
//         b: {
//             c: 'nestedC',
//             d: 'nestedD',
//         },
//         c: 'theC',
//     },
// }

setIn(path, value, targetObj)

Returns an object, with the value at path set to value. path can be a dot-separated list of attribute values or an array of attribute names to traverse.

const obj = {
    location: {
        city: 'San Francisco',
    },
};

const newObj = ops.setIn(['location', 'city'], 'Helsinki', obj);
console.log(newObj);
// {
//     location: {
//         city: 'Helsinki',
//     },
// };

omit(keysToOmit, targetObj)

Returns a shallow copy of targetObj without the keys specified in keysToOmit. keysToOmit can be a single key name or an array of key names.

const obj = {
    a: true,
    b: true,
};

const result = ops.omit('a', obj);

console.log(result);
// {
//     b: true,
// }

Array API

insert(startIndex, values, targetArray)

Returns a new array with values inserted at starting at index startIndex to targetArray.

const arr = [1, 2, 4];
const result = ops.insert(2, [3], arr);
console.log(result);
// [1, 2, 3, 4]

push(value, targetArray)

Returns a shallow copy of targetArray with value added to the end. value can be a single value or an array of values to push.

const arr = [1, 2, 3];
const result = ops.push(4, arr);
console.log(result);
// [1, 2, 3, 4]

filter(func, targetArray)

Returns a shallow copy of targetArray with items that func returns true for, when calling it with the item.

const arr = [1, 2, 3, 4];
const result = ops.filter(item => item % 2 === 0, arr);
console.log(result);
// [2, 4]

splice(startIndex, deleteCount, values, targetArray)

Like Array.prototype.splice, but operates on a shallow copy of targetArray and returns the shallow copy.

const arr = [1, 2, 3, 3, 3, 4];
const result = ops.splice(2, 2, [], arr);
console.log(result);
// [1, 2, 3, 4]

API for both Object and Array

set(key, value, target)

Returns a shallow copy of target with its value at index or key key set to value.

const arr = [1, 2, 5];
const result = ops.set(2, 3, arr);
console.log(result);
// [1, 2, 3]

const obj = {
    a: 'X',
    b: 'theB',
};
const resultObj = ops.set('a', 'theA', obj);
console.log(resultObj);
// {
//     a: 'theA',
//     b: 'theB',
// }

Changelog

0.5.0: Major Changes

• BREAKING: No getImmutableOps function, which was the main export, is exported anymore because options were removed. Now the object containing the operation functions is exported directly.

• BREAKING: removed option to choose whether operations are curried. Functions are now always curried.

• BREAKING: former batched mutations API totally replaced.

• BREAKING: batched mutations implementation changed.

  Previously newly created objects were tagged with a "can mutate" tag, and references to those objects were kept in a list. After the batch was finished, the list was processed by removing the tags from each object in the list.

  Now a batch token is created at the start of a batch (or supplied by the user). Each newly created object is tagged with that token. If a batch using token X operates on an object that is tagged with token X, it is free to mutate it. New batches use a token Y that will never be equal to the previous token.

  Tags are not removed anymore; They are assigned to a non-enumerable property @@_______immutableOpsOwnerID which should avoid any collisions.

  This token strategy is similar to what ImmutableJS uses to track batches.

License

MIT. See LICENSE