字符串集和数组之间的区别

Question

我有一个像这样的收藏

const collection = [{url: '/string/'}, {url: '/string-2/'}]

和string的array

const strings = ['/string/']

我试着在这两者之间做出区别，结果是

const difference = [{url: '/string-2/'}]

我试着用lodash _.filter

const difference = _.filter(collection, obj => strings.every(url => url !== obj.self));

但它不起作用。我尝试过使用._partition，但它确实返回了多个数组，而我只希望有一个没有对象的集合

Answer 1

通过使用.filter()并检查当前对象的url是否包含在strings数组中，您可以在不使用lodash的情况下完成此操作，如下所示：

​

const collection = [{url: '/string/'}, {url: '/string-2/'}];
const strings = ['/string/'];

const difference = collection.filter(({url}) => strings.includes(url));
console.log(difference);

​

..。或者，如果每个url都是唯一的，则更有效的方法是创建一个Map，其中映射中的每个键都是一个指向您的对象的url。然后对strings数组执行.map()操作，如下所示：

​

const collection = [{url: '/string/'}, {url: '/string-2/'}];
const strings = ['/string/'];

const collection_map = new Map(collection.map(obj => [obj.url, obj]));
const difference = strings.map(str => collection_map.get(str));
console.log(difference);

​

通过使用带有_.includes()的_.filter()方法，可以应用与上面相同的逻辑，如下所示：

​

const collection = [{url: '/string/'}, {url: '/string-2/'}];
const strings = ['/string/'];

const difference = _.filter(collection, obj => _.includes(strings, obj.url));
console.log(difference);

<script src="https://cdn.jsdelivr.net/lodash/4.16.4/lodash.min.js"></script>

​

Answer 2

试试differenceWith

const collection = [{url: '/string/'}, {url: '/string-2/'}]

const strings = ['/string/']

result = _.differenceWith(collection, strings, (a, b) => a.url === b)

console.log(result) // [ { url: '/string-2/' } ]

Answer 3

您可以使用简单的Array.prototype.includes() & Array.prototype.filter()完成此操作，如下所示：

const collection = [{url: '/string/'}, {url: '/string-2/'}];

const strings = ['/string/'];

const difference = collection.filter(c => strings.includes(c.url) );
console.log(difference)