JS计算两个数组的交集、差集、并集、补集

[madfour]

1、使用 filter、indexOf、concat

let a = [1, 2, 3, 4, 5]
let b = [2, 4, 6, 8, 10]

//交集
let c = a.filter(function (v) {
  return b.indexOf(v) > -1
})
//差集
let d = a.filter(function (v) {
  return b.indexOf(v) == -1
})
//补集
let e = a.filter(function (v) {
    return !(b.indexOf(v) > -1)
  })
  .concat(b.filter(function (v) {
    return !(a.indexOf(v) > -1)
  }))
//并集
let f = a.concat(b.filter(function (v) {
  return !(a.indexOf(v) > -1)
}));

console.log('交集', c)    // [2, 4]
console.log('差集', d)    // [1, 3, 5]
console.log('补集', e)    // [1, 3, 5, 6, 8, 10]
console.log('并集', f)    // [1, 2, 3, 4, 5, 6, 8, 10]

2、ES6 语法实现

使用扩展运算符（...）以及 Set 的特性实现

// 交集
let c = a.filter(x => new Set(b).has(x));
// 差集
let d = a.filter(x => !new Set(b).has(x));
// 补集
let e = [...a.filter(x => !new Set(b).has(x)), ...b.filter(x => !new Set(a).has(x))];
// 并集
let f = Array.from(new Set([...a, ...b]));

3、对 Array 进行扩展

//数组迭代函数
Array.prototype.each = function(fn) {
  fn = fn || Function.K;
  let a = [];
  let args = Array.prototype.slice.call(arguments, 1);
  for (let i = 0; i < this.length; i++) {
    let res = fn.apply(this, [this[i], i].concat(args));
    if (res != null) a.push(res);
  }
  return a;
};
//数组是否包含指定元素
Array.prototype.contains = function(suArr) {
  for (let i = 0; i < this.length; i++) {
    if (this[i] == suArr) {
      return true;
    }
  }
  return false;
}
//不重复元素构成的数组
Array.prototype.uniquelize = function() {
  let ra = new Array();
  for (let i = 0; i < this.length; i++) {
    if (!ra.contains(this[i])) {
      ra.push(this[i]);
    }
  }
  return ra;
};

//两个数组的交集
Array.intersect = function(a, b) {
  return a.uniquelize().each(function(o) {
    return b.contains(o) ? o : null
  });
};
//两个数组的差集
Array.minus = function(a, b) {
  return a.uniquelize().each(function(o) {
    return b.contains(o) ? null : o
  });
};
//两个数组的补集
Array.complement = function(a, b) {
  return Array.minus(Array.union(a, b), Array.intersect(a, b));
};
//两个数组并集
Array.union = function(a, b) {
  return a.concat(b).uniquelize();
};

console.log('交集', Array.intersect(a, b))    // [2, 4]
console.log('差集', Array.minus(a, b))        // [1, 3, 5]
console.log('补集', Array.complement(a, b))   // [1, 3, 5, 6, 8, 10]
console.log('并集', Array.union(a, b))        // [1, 2, 3, 4, 5, 6, 8, 10]