Sorting function not working in IE 11

Question

I have a very simple sorting function that sorts objects by index:

panoramas.sort((a, b) => {
  if (a.index > b.index) return 1
})

Input:

[
  { index: 0 },
  { index: 2 },
  { index: 1 }
]

Output:

[
  { index: 1 },
  { index: 2 },
  { index: 3 }
]

The function works in Chrome and Firefox, but not in IE (the array isn't being sorted at all.)

Is there something wrong with my function?

I *suppose* it does not sort because your function has no explicit return value in the case `a.index <= b.index`. — Martin Nyolt, Sep 07 '16 at 10:43
See [this answer](http://stackoverflow.com/a/24080786/1314743). — Martin Nyolt, Sep 07 '16 at 10:45
Do you mean IE changes the values of the object properties? I mean the example code definitely doesn't sort arrays in any browser. Notice also, that IE doesn't support ES6 arrow functions. — Teemu, Sep 07 '16 at 10:54

score 4 · Answer 1 · edited May 23 '17 at 10:29

The sorting function should return -1, 0 or 1 for the ordering.

// Your function tests for 'a.index > b.index'
// but it's missing the other cases, returning false (or 0)

panoramas.sort((a, b) => {
  if (a.index > b.index) return 1;
  if (a.index < b.index) return -1;
  return 0;
})

from Sorting in JavaScript: Shouldn't returning a boolean be enough for a comparison function?

> 0 when a is considered larger than b and should be sorted after it
== 0 when a is considered equal to b and it doesn't matter which comes first
< 0 when a is considered smaller than b and should be sorted before it

for numbers, you can use a more concise approach:

panoramas.sort((a, b) => {
   return a.index - b.index; 
   // but make sure only numbers are passed (to avoid NaN)
})

for IE11, that as noted by @teemu doesn't support arrow functions, you'll have to use a function expression:

http://caniuse.com/#feat=arrow-functions

panoramas.sort(function(a, b) {
  return a.index - b.index; 
});

thnx @MartinNyolt. had the verbose solution because I think it will be easier to understand — bfmags, Sep 07 '16 at 10:56

Sorting function not working in IE 11

1 Answers1