Some Array Works

play_with_array.js

/* Example Array Of Objects :  */

let anymalgroups = [
  {nama:"kambing", jenis: "mamalia"},
  {nama:"kerbau", jenis: "mamalia"},
  {nama:"bebek", jenis: "unggas"},
  {nama:"ayam", jenis: "unggas"}
]

/* Count Per Jenis using Array.reduce in es2015 style */
let jmlperjenis = anymalgroups.reduce((grup, arr) => {
  grup[arr.nama] = (grup[arr.nama] || 0) + 1
  return grup
},{})

/*  result :
  mamalia: 2,
  unggas: 2  
*/

/* count per specific Jenis  using Array.reduce in es2015 style */

let jmlUnggas = anymalgroups.reduce((n,arr) => {
  return n + (arr.jenis === 'unggas')
},0)

/* result : 2  */