AppSync JavaScript Support for Array.sort of objects

Question

While implementing JS resolvers in AWS AppSync, I can't find a way to sort an Array of objects.

The documentation of AppSync (https://docs.aws.amazon.com/appsync/latest/devguide/built-in-objects-functions.html) mentions that Array.prototype.sort() is supported, and indeed if I pass a simple array (of Strings, for example), it is working OK. However, for objects, I can't get it to work.

Trying an inline arrow function:

array_of_objects.sort((a, b) => (a.event_ts - b.event_ts))

fails with

"errorType": "UNSUPPORTED_SYNTAX_TYPE",
"value": "Unsupported Syntax Type: ArrowFunction"

Trying an external arrow function:

const compareFn = (a, b) => {
        return (a.event_ts - b.event_ts)
        if ( a.event_ts < b.event_ts ){
            return -1;
          }
          if ( a.event_ts > b.event_ts ){
            return 1;
          }
          return 0;
    };

array_of_objects.sort(compareFn)

It doesn't sort the array in place or return a sorted array.

Trying a function argument:

const compareFn = function(a, b) {
        return (a.event_ts - b.event_ts)
        if ( a.event_ts < b.event_ts ){
            return -1;
          }
          if ( a.event_ts > b.event_ts ){
            return 1;
          }
          return 0;
    };

array_of_objects.sort(compareFn)

Fails with:

"errorType": "UNSUPPORTED_SYNTAX_TYPE"
"value": "Unsupported Syntax Type: FunctionExpression"

I get Unsupported Syntax Type: FunctionExpression error (see in the question details). — Guy
– Guy, Commented Feb 5, 2023 at 14:29
Well a function declaration statement is not a "function expression", so I can't say what that parser is doing. A function declaration statement starts with the keyword function, while a function expression does not. — Pointy
– Pointy, Commented Feb 5, 2023 at 14:36

Raph · Accepted Answer · 2023-05-22 20:53:46Z

3

At time of writing this answer, the documentation also states that:

Note

Array.prototype.sort() doesn't support arguments.

So you are basically stuck with the default array sort, which sorts in place in ascending order :/

A bit disappointing isn't it?

I'm afraid your best guess would be to implement your own sorting function.

answered May 22, 2023 at 20:53

Raph

5547 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Theo Rogers · Accepted Answer · 2024-01-20 22:12:52Z

0

This works at the time of writing.

Since Array.sort doesnt support anonymous functions in AppSync_JS, you need to defined your sorting function first.

const sorter = (a: item, b: item ) => b.event_ts - a.event_ts

array_of_objects.sort(sorter);

edited Jan 20, 2024 at 22:12

answered Jan 20, 2024 at 22:10

Theo Rogers

111 silver badge2 bronze badges

Comments

Vivu · Accepted Answer · 2024-02-02 06:25:43Z

A quick n dirty script that can be used in aws appsync resolver. Takes care of sort, parameterised func, inline func, for & ++ constraints of appsync/js - hope it helps someone

const cfunc_=(a,b)=>a>b
function bs_(arr) {
    var i=0, j,tmp1,tmp2,tmpArr=arr.slice(),sliceArr,break_=false,len = arr.length,isSwapped = false;
    tmpArr.forEach(
        (ele)=>{
            isSwapped = false;
            sliceArr=arr.slice(0,len-i-1)
            j=0;
            sliceArr.forEach(
                (tmpEle)=>{
                  if (cfunc_(arr[j],arr[j + 1])) {
                      tmp2 = arr[j]
                      arr[j] = arr[j + 1];
                      arr[j + 1] = tmp2;
                      isSwapped = true;
                  }
                  j=j+1
               }
            )
            i=i+1
            if(!isSwapped)
                return
        }
    )
    console.log(arr)
}
var arr_=[2,5,2,8,4,7,2,9]
bs_(arr_)

Collectives™ on Stack Overflow

AppSync JavaScript Support for Array.sort of objects

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related