是否有一种方法可以在JavaScript中返回两个数组之间的差异?

例如:

var a1 = ['a', 'b'];
var a2 = ['a', 'b', 'c', 'd'];

// need ["c", "d"]

当前回答

如果你的数组包含对象,如果你想比较一个属性,就会变得有点困难。

幸运的是,lodash使用_contains和_.pluck使这非常简单:

var list1 = [{id: 1},{id: 2}];
var list1 = [{id: 1},{id: 2}, {id: 3}];

//es6
var results = list2.filter(item => {
  return !_.contains(_.pluck(list1, 'id'), item.id);
});

//es5
var results = list2.filter(function(item){
  return !_.contains(_.pluck(list1, 'id'), item.id);
});

//results contains [{id: 3}]

其他回答

使用额外的内存来做到这一点。这样你可以用更少的时间复杂度来求解,O(n)而不是O(n *n)

function getDiff(arr1,arr2){
let k = {};
let diff = []
arr1.map(i=>{
    if (!k.hasOwnProperty(i)) {
        k[i] = 1
    }
}
)
arr2.map(j=>{
    if (!k.hasOwnProperty(j)) {
        k[j] = 1;
    } else {
        k[j] = 2;
    }
}
)
for (var i in k) {
    if (k[i] === 1)
        diff.push(+i)
}
return diff
}
getDiff([4, 3, 52, 3, 5, 67, 9, 3],[4, 5, 6, 75, 3, 334, 5, 5, 6])
    function arrayDiff(a, b) {
      return a.concat(b).filter(val => !(b.includes(val)));
      //(or) return a.concat(b).filter(val => !(a.includes(val) && b.includes(val)));
    }

/ / es6方法

function diff(a, b) {
  var u = a.slice(); //dup the array
  b.map(e => {
    if (u.indexOf(e) > -1) delete u[u.indexOf(e)]
    else u.push(e)   //add non existing item to temp array
  })
  return u.filter((x) => {return (x != null)}) //flatten result
}
Array.prototype.difference = function(e) {
    return this.filter(function(i) {return e.indexOf(i) < 0;});
};

eg:- 

[1,2,3,4,5,6,7].difference( [3,4,5] );  
 => [1, 2, 6 , 7]

基于思考者的答案,但允许重复。

映射在映射值出现时增加它们,如果它们在另一个数组中,则减少它们。

任何剩余的部分都将包括在差额中。

function diff(curr, prev) { let a = curr.split('').sort(), b = prev.split('').sort(), c = arrDiff(a, b); console.log(JSON.stringify(a), '-', JSON.stringify(b), '=', JSON.stringify(c)); return c; } function arrDiff(larger, smaller) { var entries = {}; for (var i = 0; i < larger.length; i++) { entries[larger[i]] = (entries[larger[i]] || 0) + 1; } for (var i = 0; i < smaller.length; i++) { if (entries[smaller[i]]) { entries[smaller[i]] -= 1; } else { entries[smaller[i]] = (entries[smaller[i]] || 0) + 1; } } return Object.keys(entries).sort().reduce((diff, key) => { if (entries[key] > 0) { for (var i = 0; i < entries[key]; i++) { diff.push(key); } } return diff; }, []); } // Smaller is a subset of Larger console.log('Result:', JSON.stringify(diff('ENLIGHTEN', 'LENGTHEN'))); // [ I ] console.log('Result:', JSON.stringify(diff('STRENGTH', 'TENTHS'))); // [ G, R ] // Both have a unique value console.log('Result:', JSON.stringify(diff('BUBBLE', 'RUBBLE'))); // [ B, R ] .as-console-wrapper { top: 0; max-height: 100% !important; }