//在线性时间内返回数组a中也在b中的元素: 函数相交(a, b) { 返回a.filter (Set.prototype。new Set(b)); ｝ / /例如: console.log(相交([1,2,3],[2、3、4、5]));

我推荐上述简洁的解决方案，它在大输入上优于其他实现。如果在小输入上的性能很重要，请检查下面的替代方案。

备选方案和性能比较:

有关替代实现，请参阅下面的代码片段，并检查https://jsperf.com/array-intersection-comparison以进行性能比较。

function intersect_for(a, b) { const result = []; const alen = a.length; const blen = b.length; for (let i = 0; i < alen; ++i) { const ai = a[i]; for (let j = 0; j < blen; ++j) { if (ai === b[j]) { result.push(ai); break; } } } return result; } function intersect_filter_indexOf(a, b) { return a.filter(el => b.indexOf(el) !== -1); } function intersect_filter_in(a, b) { const map = b.reduce((map, el) => {map[el] = true; return map}, {}); return a.filter(el => el in map); } function intersect_for_in(a, b) { const result = []; const map = {}; for (let i = 0, length = b.length; i < length; ++i) { map[b[i]] = true; } for (let i = 0, length = a.length; i < length; ++i) { if (a[i] in map) result.push(a[i]); } return result; } function intersect_filter_includes(a, b) { return a.filter(el => b.includes(el)); } function intersect_filter_has_this(a, b) { return a.filter(Set.prototype.has, new Set(b)); } function intersect_filter_has_arrow(a, b) { const set = new Set(b); return a.filter(el => set.has(el)); } function intersect_for_has(a, b) { const result = []; const set = new Set(b); for (let i = 0, length = a.length; i < length; ++i) { if (set.has(a[i])) result.push(a[i]); } return result; }

Firefox 53的结果:

Ops/sec on large arrays (10,000 elements): filter + has (this) 523 (this answer) for + has 482 for-loop + in 279 filter + in 242 for-loops 24 filter + includes 14 filter + indexOf 10 Ops/sec on small arrays (100 elements): for-loop + in 384,426 filter + in 192,066 for-loops 159,137 filter + includes 104,068 filter + indexOf 71,598 filter + has (this) 43,531 (this answer) filter + has (arrow function) 35,588

对于只包含字符串或数字的数组，你可以做一些排序，就像其他答案一样。对于任意对象数组的一般情况，我不认为你可以避免这样做。下面将为您提供任意数量的数组的交集作为arrayIntersection的参数:

var arrayContains = Array.prototype.indexOf ?
    function(arr, val) {
        return arr.indexOf(val) > -1;
    } :
    function(arr, val) {
        var i = arr.length;
        while (i--) {
            if (arr[i] === val) {
                return true;
            }
        }
        return false;
    };

function arrayIntersection() {
    var val, arrayCount, firstArray, i, j, intersection = [], missing;
    var arrays = Array.prototype.slice.call(arguments); // Convert arguments into a real array

    // Search for common values
    firstArray = arrays.pop();
    if (firstArray) {
        j = firstArray.length;
        arrayCount = arrays.length;
        while (j--) {
            val = firstArray[j];
            missing = false;

            // Check val is present in each remaining array 
            i = arrayCount;
            while (!missing && i--) {
                if ( !arrayContains(arrays[i], val) ) {
                    missing = true;
                }
            }
            if (!missing) {
                intersection.push(val);
            }
        }
    }
    return intersection;
}

arrayIntersection( [1, 2, 3, "a"], [1, "a", 2], ["a", 1] ); // Gives [1, "a"]; 

简单性:

// Usage
const intersection = allLists
  .reduce(intersect, allValues)
  .reduce(removeDuplicates, []);


// Implementation
const intersect = (intersection, list) =>
  intersection.filter(item =>
    list.some(x => x === item));

const removeDuplicates = (uniques, item) =>
  uniques.includes(item) ? uniques : uniques.concat(item);


// Example Data
const somePeople = [bob, doug, jill];
const otherPeople = [sarah, bob, jill];
const morePeople = [jack, jill];

const allPeople = [...somePeople, ...otherPeople, ...morePeople];
const allGroups = [somePeople, otherPeople, morePeople];

// Example Usage
const intersection = allGroups
  .reduce(intersect, allPeople)
  .reduce(removeDuplicates, []);

intersection; // [jill]

好处:

泥土简单 以数据为中心的 适用于任意数量的列表 适用于任意长度的列表 适用于任意类型的值 适用于任意排序顺序 保留形状(在任何数组中首次出现的顺序) 尽可能早退出 内存安全，不影响函数/数组原型

缺点:

内存占用率较高 更高的CPU使用率 需要理解reduce 需要理解数据流

你不希望将其用于3D引擎或内核工作，但如果你在基于事件的应用程序中运行时遇到问题，那么你的设计就有更大的问题。

“filter”和“indexOf”在IE中的Array上不支持。这个怎么样:

var array1 = [1, 2, 3];
var array2 = [2, 3, 4, 5];

var intersection = [];
for (i in array1) {
    for (j in array2) {
        if (array1[i] == array2[j]) intersection.push(array1[i]);
    }
}

该函数利用字典的强大功能，避免了N^2问题。每个数组只循环一次，第三次更短的循环返回最终结果。 它还支持数字、字符串和对象。

function array_intersect(array1, array2) 
{
    var mergedElems = {},
        result = [];

    // Returns a unique reference string for the type and value of the element
    function generateStrKey(elem) {
        var typeOfElem = typeof elem;
        if (typeOfElem === 'object') {
            typeOfElem += Object.prototype.toString.call(elem);
        }
        return [typeOfElem, elem.toString(), JSON.stringify(elem)].join('__');
    }

    array1.forEach(function(elem) {
        var key = generateStrKey(elem);
        if (!(key in mergedElems)) {
            mergedElems[key] = {elem: elem, inArray2: false};
        }
    });

    array2.forEach(function(elem) {
        var key = generateStrKey(elem);
        if (key in mergedElems) {
            mergedElems[key].inArray2 = true;
        }
    });

    Object.values(mergedElems).forEach(function(elem) {
        if (elem.inArray2) {
            result.push(elem.elem);
        }
    });

    return result;
}

如果有无法解决的特殊情况，仅通过修改generateStrKey函数就可以解决。这个函数的诀窍在于，它根据类型和值唯一地表示每个不同的数据。

这个变体有一些性能改进。在任何数组为空的情况下避免循环。它还首先遍历较短的数组，因此如果它在第二个数组中找到了第一个数组的所有值，则退出循环。

function array_intersect(array1, array2) 
{
    var mergedElems = {},
        result = [],
        firstArray, secondArray,
        firstN = 0, 
        secondN = 0;

    function generateStrKey(elem) {
        var typeOfElem = typeof elem;
        if (typeOfElem === 'object') {
            typeOfElem += Object.prototype.toString.call(elem);
        }
        return [typeOfElem, elem.toString(), JSON.stringify(elem)].join('__');
    }

    // Executes the loops only if both arrays have values
    if (array1.length && array2.length) 
    {
        // Begins with the shortest array to optimize the algorithm
        if (array1.length < array2.length) {
            firstArray = array1;
            secondArray = array2;
        } else {
            firstArray = array2;
            secondArray = array1;            
        }

        firstArray.forEach(function(elem) {
            var key = generateStrKey(elem);
            if (!(key in mergedElems)) {
                mergedElems[key] = {elem: elem, inArray2: false};
                // Increases the counter of unique values in the first array
                firstN++;
            }
        });

        secondArray.some(function(elem) {
            var key = generateStrKey(elem);
            if (key in mergedElems) {
                if (!mergedElems[key].inArray2) {
                    mergedElems[key].inArray2 = true;
                    // Increases the counter of matches
                    secondN++;
                    // If all elements of first array have coincidence, then exits the loop
                    return (secondN === firstN);
                }
            }
        });

        Object.values(mergedElems).forEach(function(elem) {
            if (elem.inArray2) {
                result.push(elem.elem);
            }
        });
    }

    return result;
}

下面是underscore.js的实现:

_.intersection = function(array) {
  if (array == null) return [];
  var result = [];
  var argsLength = arguments.length;
  for (var i = 0, length = array.length; i < length; i++) {
    var item = array[i];
    if (_.contains(result, item)) continue;
    for (var j = 1; j < argsLength; j++) {
      if (!_.contains(arguments[j], item)) break;
    }
    if (j === argsLength) result.push(item);
  }
  return result;
};

来源:http://underscorejs.org/docs/underscore.html部分- 62