计算两个数组中重叠项的数量

Question

I have two arrays, of which the Remove should be removed from the List , and the number removed should be counted.

I'm using this to remove those from 'Remove' :

  let output=this.List.filter((el)=>{
    return this.Remove.indexOf(el) <0;
  })

This is working fine, but I'd like to count the number of items that have overlapped, and thus been removed in the filter.

For example, if List=['1','2','3','4','5'] and Remove=['1','4'] , count would be 2 .

Many thanks!

Answer 1

You can do this in one reduce run. For example, you can create an object and track both cleared array and a number of deleted elements:

 const a = [1,2,3,4,5,6,7]; const b = [1,4,9]; // elements to remove const c = a.reduce((acc, cur) => b.includes(cur) ? Object.assign(acc, {n: acc.n + 1}) : Object.assign(acc, {res: acc.res.concat(cur)}), { n: 0, res: []}); console.log(c) 

Answer 2

If you don't want to compare lengths as suggested in comments (which is fine...), I can propose you the following solution using a counter:

 let list = ['1', '2', '3', '4', '5'], remove = ['1', '4'], overlap = 0; let output = list.filter(el => { let bool = remove.indexOf(el) < 0; if (!bool) overlap++; return bool; }); console.log(overlap);