基于另一个对象数组的属性对对象数组进行排序

Question

i have two object arrays in js.dummy arrays are shown below.

arr1=[{'id':1,'name':'David'},
      {'id':2,'name':'Miles'},
      {'id':3,'name':'John'},];

arr2=[{'id':2,'age':22},
      {'id':3,'age':18},
      {'id':1,'age':12},];

Can i sort arr1 in same order of ids as arr2. so arr1 becomes

[{'id':2,'name':'Miles'},
      {'id':3,'name':'John'},
      {'id':1,'name':'David'},];

actual arrays have some 900 objects each.so is there any efficient method of achieving this?

Answer 1

reduce the second array to a Map indexed by id s, then use Map.get to identify the location of the id while sorting. Map s have guaranteed O(1) lookup time:

 const arr1 = [{'id':1,'name':'David'},{'id':2,'name':'Miles'},{'id':3,'name':'John'},]; const arr2 = [{'id':2,'age':22},{'id':3,'age':18},{'id':1,'age':12},]; const ids = arr2.reduce((map, { id }, i) => map.set(id, i), new Map()); arr1.sort((a, b) => ids.get(a.id) - ids.get(b.id)); console.log(arr1); 

Still, 900 objects is not much at all in the modern day.

Answer 2

// cache arr1 id to index, id is key, index is value
let arr1IdToIndex = arr1.reduce((sum, cur, index) => (sum[cur.id] = index, sum), {})
let result = arr2.map(cur => arr1[arr1IdToIndex[cur.id]])
arr1 = result