用javascript实现数组交叉的最简单、无库代码是什么?我想写
intersection([1,2,3], [2,3,4,5])
并获得
[2, 3]
用javascript实现数组交叉的最简单、无库代码是什么?我想写
intersection([1,2,3], [2,3,4,5])
并获得
[2, 3]
当前回答
如果您的环境支持ECMAScript 6 Set,一个简单而有效的方法(参见规范链接):
function intersect(a, b) {
var setA = new Set(a);
var setB = new Set(b);
var intersection = new Set([...setA].filter(x => setB.has(x)));
return Array.from(intersection);
}
更短,但可读性更差(也没有创建额外的交集集):
function intersect(a, b) {
var setB = new Set(b);
return [...new Set(a)].filter(x => setB.has(x));
}
注意,当使用Set时,你只会得到不同的值,因此new Set([1,2,3,3])。Size的值为3。
其他回答
这是一个提议的标准:对于当前阶段2的提议https://github.com/tc39/proposal-set-methods,您可以使用
mySet.intersection(mySet2);
在此之前,你可以使用Immutable.js的Set,它激发了这个提议
Immutable.Set(mySet).intersect(mySet2)
使用Underscore.js或lodash.js
_.intersection( [0,345,324] , [1,0,324] ) // gives [0,324]
“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]);
}
}
ES2015的函数式方法
函数式方法必须考虑只使用没有副作用的纯函数,每个函数只与单个作业有关。
这些限制增强了所涉及函数的可组合性和可重用性。
//小的,可重用的辅助函数 const createSet = xs => new Set(xs); Const filter = f => xs => xs.filter(apply(f)); Const apply = f => x => f(x); / /十字路口 Const相交= xs => ys => { const zs =创建集(ys); 返回过滤器(x => zs.has(x)) ? 真正的 :假 ) (x); }; //模拟数据 Const xs = [1,2,2,3,4,5]; Const ys = [0,1,2,3,3,3,6,7,8,9]; //运行 Console.log (intersect(xs) (ys));
请注意,使用本机Set类型,这有一个优点 查找性能。
避免重复
显然,第一个数组中重复出现的项将被保留,而第二个数组将被去重。这可能是也可能不是理想的行为。如果你需要一个唯一的结果,只需对第一个参数应用重复数据删除:
// auxiliary functions const apply = f => x => f(x); const comp = f => g => x => f(g(x)); const afrom = apply(Array.from); const createSet = xs => new Set(xs); const filter = f => xs => xs.filter(apply(f)); // intersection const intersect = xs => ys => { const zs = createSet(ys); return filter(x => zs.has(x) ? true : false ) (xs); }; // de-duplication const dedupe = comp(afrom) (createSet); // mock data const xs = [1,2,2,3,4,5]; const ys = [0,1,2,3,3,3,6,7,8,9]; // unique result console.log( intersect(dedupe(xs)) (ys) );
计算任意数量数组的交集
如果你想计算任意数量的数组的交点,只需用compose intersect和foldl。这是一个方便函数:
// auxiliary functions const apply = f => x => f(x); const uncurry = f => (x, y) => f(x) (y); const createSet = xs => new Set(xs); const filter = f => xs => xs.filter(apply(f)); const foldl = f => acc => xs => xs.reduce(uncurry(f), acc); // intersection const intersect = xs => ys => { const zs = createSet(ys); return filter(x => zs.has(x) ? true : false ) (xs); }; // intersection of an arbitrarily number of Arrays const intersectn = (head, ...tail) => foldl(intersect) (head) (tail); // mock data const xs = [1,2,2,3,4,5]; const ys = [0,1,2,3,3,3,6,7,8,9]; const zs = [0,1,2,3,4,5,6]; // run console.log( intersectn(xs, ys, zs) );
希望这有助于所有版本。
function diffArray(arr1, arr2) {
var newArr = [];
var large = arr1.length>=arr2.length?arr1:arr2;
var small = JSON.stringify(large) == JSON.stringify(arr1)?arr2:arr1;
for(var i=0;i<large.length;i++){
var copyExists = false;
for(var j =0;j<small.length;j++){
if(large[i]==small[j]){
copyExists= true;
break;
}
}
if(!copyExists)
{
newArr.push(large[i]);
}
}
for(var i=0;i<small.length;i++){
var copyExists = false;
for(var j =0;j<large.length;j++){
if(large[j]==small[i]){
copyExists= true;
break;
}
}
if(!copyExists)
{
newArr.push(small[i]);
}
}
return newArr;
}