从数组对象中删除重复项 - TypeScript

Question

Whats the cleanest way of removing duplicates.

0: { taxType: 9, taxCode: "a", taxValidFrom: "01 Jan 2020 00:00:00.000", taxDesc: "a", …}
1: { taxType: 9, taxCode: "C", taxValidFrom: "03 Jan 2020 00:00:00.000", taxDesc: "C", …}
2: { taxType: 9, taxCode: "a", taxValidFrom: "04 Jan 2020 00:00:00.000", taxDesc: "a", …}
3: { taxType: 9, taxCode: "C", taxValidFrom: "05 Jan 2020 00:00:00.000", taxDesc: "C", …}
4: { taxType: 9, taxCode: "B", taxValidFrom: "06 Jan 2020 00:00:00.000", taxDesc: "B", …}

I want to end up with an array where there is one entry based on date and taxcode.

So if taxcode is C, i should only have the one where the date is "05 Jan 2020 00:00:00.000", as this is the closest to todays date (06/01/2020)

Answer 1

You can loop through each object in the array and push or replace the current object.

So, the approach can be:
1. If the taxcode is not present in the final array, push the new object in the final array.
2. If the taxcode is already present in the final array, compare the date in both and keep the latest one.

Suggestion:
You can use a reduce function for the same.

 function modifyArray(arr) { return arr.reduce((acc, curr) => { const elementIndexInArray = acc.findIndex(a => a.taxCode === curr.taxCode); if(elementIndexInArray === -1) { acc.push(curr); } else if (new Date(acc[elementIndexInArray].taxValidFrom) < new Date(curr.taxValidFrom)) { acc.splice(elementIndexInArray, 1, curr); } return acc; }, []); } var a = [ { taxType: 9, taxCode: "a", taxValidFrom: "01 Jan 2020 00:00:00.000", taxDesc: "a"}, { taxType: 9, taxCode: "C", taxValidFrom: "03 Jan 2020 00:00:00.000", taxDesc: "C"}, { taxType: 9, taxCode: "a", taxValidFrom: "04 Jan 2020 00:00:00.000", taxDesc: "a"}, { taxType: 9, taxCode: "C", taxValidFrom: "05 Jan 2020 00:00:00.000", taxDesc: "C"}, { taxType: 9, taxCode: "B", taxValidFrom: "06 Jan 2020 00:00:00.000", taxDesc: "B"} ]; console.log(modifyArray(a));