过滤数组返回空

Question

I'm trying to populate an array with all values retrieved (I am in a loop) and then to delete values already present in the yearsJustSelected array:

yearsJustSelected.forEach((el:any)=>{
    yearsJustSelectedAll.push(el);
  });


  yearsJustSelectedFiltered = yearsJustSelected.filter((el: any) => !yearsJustSelectedAll.includes(el));

For example:
loop 1 --> yearsJustSelected=[1, 2, 3] - yearsJustSelectedAll=[1, 2, 3] - yearsJustSelectedFiltered = []
loop 2 --> yearsJustSelected=[2, 3, 4, 5] - yearsJustSelectedAll=[1, 2, 3, 4, 5] - yearsJustSelectedFiltered=[4, 5] --> because [2, 3 ] were already present in the yearsJustSelectedAll in the first loop

This code:

yearsJustSelectedFiltered = yearsJustSelected.filter((el: any) => !yearsJustSelectedAll.includes(el));

always return an empty array.

Answer 1

  yearsJustSelected.forEach((el:any)=>{
    yearsJustSelectedAll.push(el);
  });
// The code above will add all elements in yearsJustSelected into yearsJustSelectedAll
// making the two arrays the same.

There are no instances where one array has elements that are not in the other array

Answer 2

You could check if the target array does not have the item. Then push the item to the target array.

 function select(source, target) { source.forEach(v => target.includes(v) || target.push(v)); } var yearsJustSelectedAll = []; select([1, 2, 3], yearsJustSelectedAll); console.log(...yearsJustSelectedAll); select([2, 3, 4, 5], yearsJustSelectedAll); console.log(...yearsJustSelectedAll); select([4, 5], yearsJustSelectedAll); console.log(...yearsJustSelectedAll);