如何防止以下map函数返回未定义的对象？

Question

I have a function loops through an array, rearranges its objects, and returns the result (excluding the current object):

// buildings = [{ objectId: '1', objectId: '2', objectId: '3' }]
// currentBuilding = { objectId: '1' }
const result buildings.map(building => {
  if (building.objectId === this.currentBuilding.objectId) {
    return
  }
  return {
    newField: building.objectId,
  }
})
return result

I want it to return:

This function will return:

[{ newField: '2', newField: '3' }]

However, now I'm getting:

[{ undefined, newField: '2', newField: '3' }]

Why is this and how to fix it?

Answer 1

You can't, but you can filter out the offending item:

const result buildings.filter(b => b.objectId !== this.currentBuilding.objectId)
                      .map(b => ({newField: b.objectId});