Es6 utilities

Filter

Info

The filter() method take an arg function with array element like parameter. The function return a booleanfilter. An second parameter may be used for element indice. Filter return an array.

Simple Example

const users = ['John', 'Marc', 'Mattew', 'Peter', 'Paul'];
const result = users.filter(user => user.length > 4);
// return name length > 4
// result return: Array["Mattew", "Peter"]

const result = users.filter((user, i) => i > 2);
// return indice > 2
// result return: Array["Peter", "Paul"]

Filter example with an object

Intial data

const users = {
  "admin": false,
  "user": true,
  "super": true
}

Output all true data from user object

Solution

Object.keys(users).filter(
  (k) => {
    return user[k]
  }
);
// Output: [ 'user', 'super' ]

shortland solution

Object.keys(users).filter(
  (k) => user[k]
);
// Output: [ 'user', 'super' ]

Map

Info

map take an arg function with array element like parameter. The function must return the new value. An second parameter may be used for element indice. Map return an array.

Simple Example

const users = ['John', 'Marc', 'Mattew', 'Peter', 'Paul'];
const result = users.filter(user => user.length > 4);
// result return: Array["Mattew", "Peter"]

const result = users.filter((user, i) => i > 2);

Reduce

Info

The reduce() method executes a user-supplied "reducer" callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements of the array is a single value.

Simple Example

const array1 = [1, 2, 3, 4];
const reducer = array1.reduce((acc, element) => acc + element);
// return 10

const reducer2 = array1.reduce((acc, element, i) => acc + element + i);
// return 16

Reduce Exemple

Intial data

const pilots = [
  {
    id:10,
    name: "Peo Dameron",
    years: 30,
  },
  {
    id:2,
    name: "Temin Wexley",
    years: 50,
  },
  {
    id:41,
    name: "Tallissan Lintra",
    years: 13,
  },
  {
    id:99,
    name: "Ello Asty",
    years: 5,
  },
];

Get the lower age pilot

const pilot = pilots.reduce(
    (acc, element) => (acc.years || 0) < element.years ? acc : element
);

// Output : { id: 99, name: 'Ello Asty', years: 5}

More reduce practices