ts-options-defaults

ts-options-defaults

Object.assign({}, defaults, options) and equivalent with destructing {...defaults, ...options} come with a pitfall of creating only a shallow copy. Lodash _.merge works on deep properties, but it merges arrays and that usually makes no sense in the context of default options (also it mutates first element; this package doesn't). This package fixes that problem - it merges objects deeply and overrides arrays. Also result remains strongly typed.

Options-defaults design pattern implementation for reliable configuration.

Usage

npm i ts-options-defaults

Design pattern

import { defaults } from 'ts-options-defaults';

export interface ISomeOptions {
    logger?: Partial<Console>;
    path: string;
}

export class Something {
    static defaults: Required<ISomeOptions> = {
        logger: console,
    };

    constructor(public options: IRatOptions) {
        this.options = defaults({}, Rat.defaults, options);
    }
}

Behavior

import { defaults } from 'ts-options-defaults';

const someDefaults = {
    some: {
        nested: {
            property: 'default',
            shouldStay: 'default',
            array: ['default1', 'default2'],
        },
    },
    array: ['default'],
};

const someOptionsOne = {
    some: {
        nested: {
            property: 'overriden',
            array: ['overriden1'],
        },
    },
    array: ['overriden'],
};

const someOptionsTwo = {
    justAddingThisOne: true,
};

const options = defaults(someDefaults, someOptionsOne, someOptionsTwo);
// options will be:
// {
//     "some": {
//         "nested": {
//             "property": "overriden",
//             "shouldStay": "default",
//             "array": [
//                 "overriden1"
//             ]
//         }
//     },
//     "array": [
//         "overriden"
//     ],
//     "justAddingThisOne": true
// }
//
// someDefaults will not be mutated!