Useful JavaScript snippets

Functional programming

Construct a new object with reduce

const allItems = ['item1', 'item2', 'item3', 'item4', 'item5', 'item6'];
const selected = { item2: 2, item4: 2, item6: 1 };

const result = allItems.reduce((acc, item) => ({
	...acc,
	[item]: selected[item] ? selected[item] : 0,
}), {})

console.log('func',result)

Flatten an array of items with reduce and Set

export const flattenItems = (items) => {
  const result = items.reduce( (prev, next) => prev.concat(next.subItems), []);
  return [...new Set(result)];
}

Total items with reduce

items.reduce((acc, item) => acc + item.price, 0);

Unique values using Set

const uniqueArray = [...new Set([5,5,2,4,2])];

Closures

function makeAdjectifier(adjective) {
  return function (noun) {
    return adjective + ' ' + noun;
  }
}

const adjective = makeAdjectifier('hello')
adjective('JS')

Pipe and Compose

const pipe = (...fns) => x => fns.reduce((v, f) => f(v), x)

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x);

ImmutableJS - create list

const Imjs = require('immutable);

const a = Imjs.List.of(1,2); // [1, 2]
const a2 = a.push(3);        // [1, 2, 3]
a.size;                      // 2
a2.get(2);                   // 3

ImmutableJS - create map

const Imjs = require('immutable);

const o = Imjs.Map({"a": 1, "b": 2}); // {"a": 1, "b": 2}
const o2 = o.set("a", 3);             // {"a": 3, "b": 2}
o.get("a");                           // 1
o2.get("a");                          // 3

tabrezakhtar/js-snippets

Useful JavaScript snippets

Functional programming