intersections from more than two arrays

intersection.js

// 2 March 2023
// intersections from more than two arrays

// goaded by https://frontendroom.com/intersection-of-multiple-arrays-in-js/

// works on arrays of values and arrays of objects with a single key;
// not sure I agree with the multiple keys matching output.

// values
var a = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7"]
var b = ["Item 6", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7"]
var c = ["Item 4", "Item 7", "Item 5", "Item 6", "Item 8", "Item 9"]
var d = ["Item 7", "Item 5", "Item 6", "Item 8", "Item 9", "Item 10"]
var e = ["Item 6", "Item 7", "Item 5", "Item 8", "Item 9", "Item 10"]

// objects
var p = [
  { name: "Item 1" },
  { name: "Item 2" },
  { name: "Item 3" },
  { name: "Item 4" },
  { name: "Item 5" },
  { name: "Item 6" },
  { name: "Item 7" },
]
var q = [
  { name: "Item 6" },
  { name: "Item 3" },
  { name: "Item 4" },
  { name: "Item 5" },
  { name: "Item 6" },
  { name: "Item 7" },
]

var r = [
  { name: "Item 4" },
  { name: "Item 7" },
  { name: "Item 5" },
  { name: "Item 6" },
  { name: "Item 8" },
  { name: "Item 9" },
]

var s = [
  { name: "Item 7" },
  { name: "Item 5" },
  { name: "Item 6" },
  { name: "Item 8" },
  { name: "Item 9" },
  { name: "Item 10" },
]
var t = [
  { name: "Item 6" },
  { name: "Item 7" },
  { name: "Item 5" },
  { name: "Item 8" },
  { name: "Item 9" },
  { name: "Item 10" },
]

function intersection(props, ...rest) {
  var [first, rest] = Array.isArray(props)
    ? [props, rest]
    : [rest[0], rest.slice(1)];

  var visited = [...first];

  Array.isArray(props.keys)
    ? props.keys.forEach(function(key) {
        visited.forEach(function(v, i) {
          rest.forEach(function(a) {
            if (!a.some(o => v[key] === o[key])) {
              visited.splice(i, 1);
            }
          });
        });
      })
    : visited.forEach(function(v, i) {
        rest.forEach(function(a) {
          if (!a.some(o => v === o)) {
            visited.splice(i, 1);
          }
        });
      });

  return visited;
}

console.log(
    intersection(a, b, c, d, e)
);

// ['Item 5', 'Item 6', 'Item 7']

console.log(
    JSON.stringify(intersection({ keys: ["name"] }, p, q, r, s, t), null, 2)
);

/*
[
  {
    "name": "Item 5"
  },
  {
    "name": "Item 6"
  },
  {
    "name": "Item 7"
  }
]
 */


console.log(
  JSON.stringify(
    intersection({ keys: ['a', 'b'] },
      [{a: 'a', b: 'b', extra: "stuff" },
       {a: 'a', b: 'b', c: 'd'},
       {a: 'no', b: 'b', c: 'e'},
       {a: 'a', b: 'no', c: 'f'},
      ],
      [{a: 'a', b: 'b'}],
      [{a: 'a', b: 'b'}],
    ), null, 2
  )
);

/*
[
  {
    "a": "a",
    "b": "b",
    "extra": "stuff"
  },
  {
    "a": "a",
    "b": "b",
    "c": "d"
  }
]
 */