Scoped Values

A JavaScript library that simulates Kotlin's scoped functions.

Inspired by Kotlin scope functions, this library can wrap any JavaScript value and provide let, also, and run functions to it.

Installation

npm install scoped-values

Usage

import $$ from "scoped-values";

const data = {
    obj: {
        a: 1
    },
    arr: [1, 2, 3],
    val: 10,
}

const doubleValue = $$(data.val).let(it => it * 2).value // 20
const undefinedValue = $$(data.undefined_value).let(it => it * 2) // undefined

$$(data.obj)
    .let((it) => {...it, b: 2})
    .run(it => console.log(it));
// console output: { a: 1, b: 2 }

$$(data.arr)
    .let((it) => [0, ...it])
    .map(it => it * 2)
    .filter(it => it < 5)
    .also(it => console.log(it));
// console output: [0, 2, 4]

Check test/index.test.js for more use cases.

ScopeValue API Reference

TL;DR

| method | fn param | return value | | ----------- | ------------- | ------------- | | .let(fn) | context value | fn result | | .also(fn) | context value | context value | | .run(fn) | context value | undefined |

Methods

.let(fn: Function): ScopeValue

Applies the provided function fn to the context value and returns a new ScopeValue instance containing the result of the function. Use this when you wish to transform the current value.

$$(1).let((it) => it + 1); // returns $$(2)

$$(null).let((it) => it + 1); // returns $$(null)

$$([1, 2]).let((it) => [...it, 3]); // return [1, 2, 3]

.also(fn: Function): ScopeValue

Applies the provided function fn to the context value without transforming it. This method returns the original ScopeValue instance. Useful for multiple operatations to the context value in a chain calls.

$$(1).also((it) => it + 1); // returns $$(1)

$$({}).also((it) => {
  it.x = 1;
}); // returns $$({ x: 1})

$$([1, 2]).also((it) => it.push(3)); // return [1, 2, 3]

.run(fn: Function)

Invokes the provided function fn using the context value. It doesn't return a value. This is mainly used for executing side effects based on the context value.

$$(1).run((it) => console.log(1)); // output: 1

Properties

.value

Returns the raw value contained within the ScopeValue context. This allows you to retrieve the unwrapped value after performing operations using the let and also methods.

License

MIT

LICENSE:

MIT License

Copyright (c) 2023 Jinyu Liu

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.