如何在数组的原始位置插入已删除的元素？

Question

In the below code:

1. First I create an array of 10 elements
2. Next I remove 3 random elements from that array.
3. I try to add those 3 random elements into the original array in the original positions.

For some reason in step 3 above (in the FINAL ARR console log), the elements are being added in the wrong position. Is my slice function incorrect in step 3? If so, how do I modify it to be correct?

 // Step 1. Create array of 10 elements const originalValues = maxAmount => { let finalArray = []; for (let i = 0; i < maxAmount; i++) { finalArray.push({ key1: `key1-${i+1}`, position: i }); } return finalArray; } let finalArr = originalValues(10); const finalArrOriginalLength = finalArr.length; //Step 2. Remove 3 random elements in this case key1-2, key1-7, key1-8 const removedElements = []; finalArr = finalArr.filter(elem => { if (elem.key1 === 'key1-7' || elem.key1 === 'key1-2' || elem.key1 === 'key1-8') { removedElements.push(elem); return false; } else { return true; } }); /* Step 3. Add those 3 elements back to the original positions */ removedElements.forEach(elem => { finalArr.splice(elem.position - (finalArrOriginalLength - finalArr.length) + 1, 0, elem); }); /* The inserted elements from step 3 are being inserted in the wrong position as seen when this console.log prints out finalArr */ console.log('FINAL ARR', finalArr);

Answer 1

There's no need to subtract from elem.position .

If you sort the removed elements by the original positions, you should be able to insert them at those positions.

This assumes there haven't been any other changes to the array.

 // Step 1. Create array of 10 elements const originalValues = maxAmount => { let finalArray = []; for (let i = 0; i < maxAmount; i++) { finalArray.push({ key1: `key1-${i+1}`, position: i }); } return finalArray; } let finalArr = originalValues(10); const finalArrOriginalLength = finalArr.length; //Step 2. Remove 3 random elements in this case key1-2, key1-7, key1-8 const removedElements = []; finalArr = finalArr.filter(elem => { if (elem.key1 === 'key1-7' || elem.key1 === 'key1-2' || elem.key1 === 'key1-8') { removedElements.push(elem); return false; } else { return true; } }); /* Step 3. Add those 3 elements back to the original positions */ removedElements.sort((a, b) => a.position - b.position).forEach(elem => { finalArr.splice(elem.position, 0, elem); }); console.log('FINAL ARR', finalArr);

Answer 2

Try this...

 // Step 1. Create array of 10 elements const originalValues = maxAmount => { let finalArray = []; for (let i = 0; i < maxAmount; i++) { finalArray.push({ key1: `key1-${i+1}`, position: i }); } return finalArray; } let finalArr = originalValues(10); const finalArrOriginalLength = finalArr.length; //Step 2. Remove 3 random elements in this case key1-2, key1-7, key1-8 const removedElements = []; finalArr = finalArr.filter(elem => { if (elem.key1 === 'key1-7' || elem.key1 === 'key1-2' || elem.key1 === 'key1-8') { removedElements.push(elem); return false; } else { return true; } }); // Step 3. Add those 3 elements back to the original positions removedElements .sort((a,b)=>{return a.position > b.position ? 0 : 1 }); removedElements.forEach(elem => { finalArr.splice(elem.position, 0, elem); }); /* The inserted elements from step 3 are being inserted in the wrong position as seen when this console.log prints out finalArr */ console.log('FINAL ARR', finalArr);