fmute

fmute is a set of functions to mutate data without changing the source. The reason of this library is to have pure javascript objects, mutate it in functional way and do not waste memory for immutable object wrappers.

Library is written in TypeScript and provide it's own type definitions. fmute/* exports as commonjs module. ES6 build also included.

Exports

The default export of library is Chain function. chain, merge, remove, set and set-in have default exports. You able to import everything from 'fmute' or just only you need from 'fmute/*'.

Functions

Array/insert

function insert<T>(source: T[], index: number, ...values: T[]): T[];

Adds one or more elements before provided index of an array.

import { insert } from 'fmute/array';
const a = ['a', 'b', 'c'];
insert(a, 1, 'x'); // returns ['a', 'x', 'b', 'c']

Array/pop

function pop<T>(source: T[], f?: (v: T) => void): T[];

Removes the last element from an array, callback called with that element.

import { pop } from 'fmute/array';
const a = ['a', 'b', 'c'];
pop(a); // returns ['a', 'b']

Array/push

function push<T>(source: T[], ...values: T[]): T[];

Adds one or more elements to the end of an array.

import { push } from 'fmute/array';
const a = ['a', 'b', 'c'];
push(a, 'x', 'y'); // returns ['a', 'b', 'c', 'x', 'y']

Array/reverse

function reverse<T>(source: T[]): T[];

Reverses order of elements in an array.

import { reverse } from 'fmute/array';
const a = ['a', 'b', 'c'];
reverse(a); // returns ['c', 'b', 'a']

Array/shift

function shift<T>(source: T[], f?: (v: T) => void): T[];

Removes the first element from an array, callback called with that element.

import { shift } from 'fmute/array';
const a = ['a', 'b', 'c'];
shift(a); // returns ['b', 'c']

Array/unshift

function unshift<T>(source: T[], ...values: T[]): T[];

Adds one or more elements to the beginning of an array.

import { unshift } from 'fmute/array';
const a = ['a', 'b', 'c'];
unshift(a, 'x', 'y'); // returns ['x', 'y', 'a', 'b', 'c']

Array/splice

function splice<T>(source: T[], start: number, deleteCount: number, ...items: T[]): {
    removed: T[];
    array: T[];
};

Removes existing elements and addes new. Returns object with removed elements and new result.

import { splice } from 'fmute/array';
const a = ['a', 'b', 'c', 'd', 'e'];
splice(a, 1, 2, 'x', 'y');
// returns {
//     removed: ['b', 'c'],
//     array: ['a', 'x', 'y', 'd', 'e']
// }

set

function set(source: any, path: string | (string | number)[], value: any): any;

Returns copy of a source with new property set by provided path.

import { set } from 'fmute/set'; // or import set from 'fmute/set';
const source = {
    a: {
        b: 1
    },
    c: {
        d: 2
    }
};
set(source, 'a.b', 3); // or set(source, ['a', 'b'], 3);
// returns {
//     a: {
//         b: 3
//     },
//     c: {
//         d: 2
//     }
// }

// also, works with arrays:
const table = [
    [1, 2],
    [3, 4]
];

set(table, [1, 1], 5);
// returns [
//     [1, 2],
//     [3, 5]
// ];

setIn

function setIn(source: any, path: string | (string | number)[], fn: (value: any) => any): any;

Returns copy of a source with new property set by provided path. Instead of new value expects a reducer.

import { setIn } from 'fmute/set-in'; // or import set from 'fmute/set-in';
const source = {
    a: {
        b: {
            c: {
                d: 1
            }
        }
    }
};
setIn(source, 'a.b', (branch) => {  // or setIn(source, ['a', 'b']...
    // branch will be {
    //     c: {
    //         d: 1
    //     }
    // }
    return {
        ...branch,
        foo: 'bar'
    }
});
// returns {
//     a: {
//         b: {
//             c: {
//                 d: 1
//             },
//             foo: 'bar'
//         }
//     }
// }

remove

function remove(source: any, path: string | (string | number)[]): any;

Removes branch from object. Does not change array's length.

import { remove } from 'fmute/remove'; // or import remove from 'fmute/remove';
const source = {
    a: {
        b: {
            c: {
                d: 1
            }
        }
    }
};
remove(source, 'a.b');  // or remove(source, ['a', 'b'])
// returns {
//     a: {
//     }
// }

merge

function function merge(to: any, from: any): any;

Merges second object into first. If you need to remove branch - use special type Delete.

import { merge, Delete } from 'fmute/merge'; // or import merge, { Delete } from 'fmute/merge';
const source = {
    a: {
        b: 1
    },
    c: {
        d: 2
    }
};
merge(source, {
    a: {
        foo: 'bar'
    },
    c: {
        d: Delete,
        x: 'y'
    }
});
// returns {
//     a: {
//         b: 1,
//         foo: 'bar'
//     },
//     c: {
//         x: 'y'
//     }
// }

chain

function Chain(source?: any): ChainInstance;

Chains mutations and memorizes it. You able to apply this mutations to any object you want. Calling Chain creates new ChainInstance object, every method call creates new instance, exept exec, which returns a result.

Here is class definition:

class ChainInstance {
    constructor(source?: any);
    set(path: string | (string | number)[], value: any): ChainInstance;
    remove(path: string | (string | number)[]): ChainInstance;
    merge(source: any): ChainInstance;
    apply(fn: (state: any) => any): ChainInstance;
    setIn(path: string | (string | number)[], fn: (value: any) => any): ChainInstance;
    exec(source?: any): any;
}

Example:

import { Chain, Delete } from 'fmute';

const source = {
    a: {
        c: {
            v: 100,
            d: 300
        },
        e: [
            100,
            {
                x: 200
            },
            300
        ]
    },
    b: {
        d: {
            u: 200
        }
    }
};

let chain = Chain()
    .set('a.c.r', 100)
    .remove('b.d.u')
    .merge({ a: { c: { d: Delete } }, b: { d: { w: { q: 'a', p: 'b' } } } })
    .apply((state) => ({ ...state, p: { w: 100 } }))
    .set('p.e', 200)
    .setIn('b.d', s => ({ ...s, y: 'b' }))
    .set('a.x', 100);

chain.exec(source); // or Chain(source) and then just .exec();
// returns {
//     a: {
//         c: {
//             v: 100,
//             r: 100
//         },
//         e: [
//             100,
//             {
//                 x: 200
//             },
//             300
//         ],
//         x: 100
//     },
//     b: {
//         d: {
//             w: {
//                 q: 'a',
//                 p: 'b'
//             },
//             y: 'b'
//         }
//     },
//     p: {
//         w: 100,
//         e: 200
//     }
// }