Javascript sort custom comparator function - sorting a sorted array

Question

I have an array of objects of the following form:

arr[0] = { 'item1' : 1234, 'item2' : 'a string' }; 

I sort it first by 'item1' which is straightforward. Now i want to sort arr (which is sorted by 'item1') again but this time by 'item2' but only for the elements where 'item1' is the same. The final array would look like:

arr = [   { 'item1' : 1234, 'item2' : 'apple' },   { 'item1' : 1234, 'item2' : 'banana' },   { 'item1' : 1234, 'item2' : 'custard' },   { 'item1' : 2156, 'item2' : 'melon' },   { 'item1' : 4345, 'item2' : 'asparagus' }  ]; 

I tried to write a sorting function for the second case like so:

arr.sort(function(a,b){   if(a.item1 === b.item1){     return a.item2 > b.item2 ? 1 : a.item2 < b.item2 : -1 : 0;   } }); 

I could combine the two sorts in one function to get the final sorted array but there will be cases where I'll have to sort by just 'item1' or just 'item2'.

Answer 1

You can have four different comparison functions - one sorting by item1, one by item2, one by item1 then item2 and one by item2 then item1.

E.g.:

arr.sort(function(a,b){   if(a.item1 == b.item1){     return a.item2 > b.item2 ? 1 : a.item2 < b.item2 ? -1 : 0;   }    return a.item1 > b.item1 ? 1 : -1; });