nulless v0.2.3

nulless

nulless is a javascript/typescript library that helps you handle null/undefined safely and elegance. nulless provide a class called Maybe to wrap your value, the concept comes from Monad. Maybe has serval functions to handle null check and support chain call, it can also support async with rxjs.

Usage

basics usage:

import { Maybe } from 'nulless';

let maybe = Maybe.nothing();
console.log(maybe.getDangerValue() === null); // => true
console.log(maybe.transform((value) => value + 'inside').isNothing()); // => true, because maybe has no value
maybe.do(value => console.log(value)) // => do nothing, because maybe has no value

maybe = Maybe.just(43);
console.log(maybe.getDangerValue()); // => 43
console.log(maybe.transform(value => value + 'inside').getValue()); // => 43inside
maybe.do(value => console.log(value)); // => 43

code without nulless:

let items = [{id: 1, content: {subContent: 2}}, {id: 2, content: null}, {id: 4, content: {subContent: 6}}];
function getItemSubContent(id) {
    if (!id) return null;

    let item = items.find(e => e.id === id);
    if (!item) return null;
    if (!item.content) return null;

    return item.content.subContent;
}

let v1 = getItemSubContent(null);
if (v1) {
    console.log(v1);
}
let v2 = getItemSubContent(1);
if (v2) {
    console.log(v2);
}
let v3 = getItemSubContent(2);
if (v3) {
    console.log(v3);
}
let v4 = getItemSubContent(3);
if (v4) {
    console.log(v4);
}

code with nulless:

import { Maybe } from 'nulless';

let items = [{
    id: 1,
    content: {
        subContent: 'dsa'
    }
}, {
    id: 2,
    content: null
}, {
    id: 4,
    content: {
        subContent: 'fd'
    }
}];

function getItemSubContent(id) {
    // function transform will return another maybe
    return id.transform(value => items.find(item => item.id === value))
        .transform(value => value.content)
        .transform(value => value.subContent);
}

// function do will call pass-in function if maybe has value
getItemSubContent(Maybe.nothing()).do(value => console.log(value)); // do nothing since get nothing
getItemSubContent(Maybe.just(1)).do(value => console.log(value)); // => dsa, since get actual value
getItemSubContent(Maybe.just(2)).do(value => console.log(value)); // do nothing since get nothing
getItemSubContent(Maybe.just(3)).do(value => console.log(value)); // do nothing since get nothing

async nulless with rxjs:

import { Maybe } from 'nulless';
import { Observable } from 'rxjs';

function getItemSubContent(id) {
    // function transform will return another maybe
    return id.asyncTransform(value => new Observable(subscriber => {
        let items = [{
            id: 1,
            content: {
                subContent: 'dsa'
            }
        }, {
            id: 2,
            content: null
        }, {
            id: 4,
            content: {
                subContent: 'fd'
            }
        }];
        let result = Maybe.just(items.find(item => item.id === value))
            .transform(value => value.content)
            .transform(value => value.subContent);
        subscriber.next(result);
    }));
}

// function do will call pass-in function if maybe has value
getItemSubContent(Maybe.nothing()).subscribe(value => console.log(value)); // do nothing since get nothing id
getItemSubContent(Maybe.just(1)).subscribe(value => console.log(value)); // => dsa, since get actual value
getItemSubContent(Maybe.just(2)).subscribe(value => console.log(value)); // => nothing maybe, since get nothing item
getItemSubContent(Maybe.just(3)).subscribe(value => console.log(value)); // => nothing maybe, since get nothing item

Install

npm install nulless