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
我扩展了tarulen的答案,以适用于任何数量的数组。它也应该适用于非整数值。
function intersect() {
const last = arguments.length - 1;
var seen={};
var result=[];
for (var i = 0; i < last; i++) {
for (var j = 0; j < arguments[i].length; j++) {
if (seen[arguments[i][j]]) {
seen[arguments[i][j]] += 1;
}
else if (!i) {
seen[arguments[i][j]] = 1;
}
}
}
for (var i = 0; i < arguments[last].length; i++) {
if ( seen[arguments[last][i]] === last)
result.push(arguments[last][i]);
}
return result;
}
其他回答
“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]);
}
}
这是我使用的一个非常简单的实现。它是无损的,也确保不复制整个。
Array.prototype.contains = function(elem) {
return(this.indexOf(elem) > -1);
};
Array.prototype.intersect = function( array ) {
// this is naive--could use some optimization
var result = [];
for ( var i = 0; i < this.length; i++ ) {
if ( array.contains(this[i]) && !result.contains(this[i]) )
result.push( this[i] );
}
return result;
}
基于Anon的出色回答,这个函数返回两个或多个数组的交集。
function arrayIntersect(arrayOfArrays)
{
var arrayCopy = arrayOfArrays.slice(),
baseArray = arrayCopy.pop();
return baseArray.filter(function(item) {
return arrayCopy.every(function(itemList) {
return itemList.indexOf(item) !== -1;
});
});
}
这是一个现代和简单的ES6方式来做,也非常灵活。 它允许您指定多个数组作为与主题数组进行比较的数组,并且可以在包含和独占模式下工作。
// =======================================
// The function
// =======================================
function assoc(subjectArray, otherArrays, { mustBeInAll = true } = {}) {
return subjectArray.filter((subjectItem) => {
if (mustBeInAll) {
return otherArrays.every((otherArray) =>
otherArray.includes(subjectItem)
);
} else {
return otherArrays.some((otherArray) => otherArray.includes(subjectItem));
}
});
}
// =======================================
// The usage
// =======================================
const cheeseList = ["stilton", "edam", "cheddar", "brie"];
const foodListCollection = [
["cakes", "ham", "stilton"],
["juice", "wine", "brie", "bread", "stilton"]
];
// Output will be: ['stilton', 'brie']
const inclusive = assoc(cheeseList, foodListCollection, { mustBeInAll: false }),
// Output will be: ['stilton']
const exclusive = assoc(cheeseList, foodListCollection, { mustBeInAll: true })
实例:https://codesandbox.io/s/zealous-butterfly-h7dgf?fontsize=14&hidenavigation=1&theme=dark
如果只使用关联数组呢?
function intersect(a, b) {
var d1 = {};
var d2 = {};
var results = [];
for (var i = 0; i < a.length; i++) {
d1[a[i]] = true;
}
for (var j = 0; j < b.length; j++) {
d2[b[j]] = true;
}
for (var k in d1) {
if (d2[k])
results.push(k);
}
return results;
}
编辑:
// new version
function intersect(a, b) {
var d = {};
var results = [];
for (var i = 0; i < b.length; i++) {
d[b[i]] = true;
}
for (var j = 0; j < a.length; j++) {
if (d[a[j]])
results.push(a[j]);
}
return results;
}