Mystery NPM | npm.io

Mystery

Flawless arrays processing.

Install

npm i mystery --save

Why?

When you use forEach, map, filter you have 2 conses to think about:

it is not as simple as could be add and remove elements in the middle of array
you should pass through the array again and again

This is where mystery shows up it's proses. It processes elements of an array one-by-one. So you have only one array walk. Similar to the way of node.js stream works, mystery is something like pipe it joins all transforms which are event emitters from the inside.

How to use?

const mystery = require('mystery');
const {map, filter, take, append, insert} = mystery;
const mapper = mystery([
    map((a) => a * a)),
    filter((a) => a > 10)),
    take(2),
    append(['yes', 'you', 'can']),
    insert(4, 'definitely')
]);

mapper([1, 2, 3, 4, 5], (array) => {
    console.log(array);
    // returns
    [16, 25, 'yes', 'you', 'definitely', 'can']
});

Transforms

You can use any of built-in transforms or write your own. Consder simple head and tail transforms which returns first and rest elements.

This is how head transform could look like:

const mystery = require('mystery');

const head = () => {
    return (value, index, emit) => {
        if (!index)
            emit(value);
    }
};

const first = mystery([
    head()
]);

first([1, 2, 3, 4, 5], (array) => {
    console.log(array);
    // result
    [1]
});

And here is tail:

const mystery = require('mystery');

const tail = () => {
    return (value, index, emit) => {
        if (index)
            emit(value);
    }
};

const rest = mystery([
    tail()
]);

first([1, 2, 3, 4, 5], (array) => {
    console.log(array);
    // returns
    [2, 3, 4, 5]
});

You can find more examples at lib/transforms.