JavaScript array of objects contains the same array data

Question

I try to get all same data values into an array of objects. This is my input:

var a = [{
    name: "Foo",
    id: "123",
    data: ["65d4ze", "65h8914d"]
  },
  {
    name: "Bar",
    id: "321",
    data: ["65d4ze", "894ver81"]
  }
]

I need a result like:

["65d4ze"]

I try to loop on my object to get this output, but I'm completely lost... I don't know how to know if the result is into all data arrays.

var a = [{
        name: "Foo",
        id: "123",
        data: ["65d4ze", "65h8914d"]
      },
      {
        name: "Bar",
        id: "321",
        data: ["65d4ze", "894ver81"]
      }
    ],
  b = [],
  c = []
a.forEach(function(object) {
  b.push(object.data.map(function(val) {
    return val;
    })
  );
});

console.log(b);

Answer 1

You could map data and get the common values with Array#map, Array#reduce, Array#filter, Set and Set#has.

var array = [{ name: "Foo", id: "123", data: ["65d4ze", "65h8914d"] }, { name: "Bar", id: "321", data: ["65d4ze", "894ver81"] }],
    key = 'data',
    common = array
        .map(o => o[key])
        .reduce((a, b) => b.filter(Set.prototype.has, new Set(a)));

console.log(common);

Answer 2

You can use the Array#filter method. Filter the first array by checking if a value is present in all other object properties (arrays), using the Array#every method to check if a value is present in all remaining arrays.

let res = a[0].data.filter(v => a.slice(1).every(a => a.data.includes(v)));

var a = [{
    name: "Foo",
    id: "123",
    data: ["65d4ze", "65h8914d"]
  },
  {
    name: "Bar",
    id: "321",
    data: ["65d4ze", "894ver81"]
  }
];

let res = a[0].data.filter(v => a.slice(1).every(a => a.data.includes(v)));

console.log(res)