I am trying to convert the below function into arrow function using ES6,

$scope.sum = function(list, prop){
  return list.reduce( function(a, b){
     return a + b[prop];
  }, 0);
};

I tried below,

$scope.sum = (list,prop) =>  {return list.reduce((a,b) => {return (a+ b[prop])}, 0)};

throwing this error Cannot read property 'reduce' of undefined

i am using in angular 1.5

I am trying to convert the below function into arrow function using ES6,

$scope.sum = function(list, prop){
  return list.reduce( function(a, b){
     return a + b[prop];
  }, 0);
};

I tried below,

$scope.sum = (list,prop) =>  {return list.reduce((a,b) => {return (a+ b[prop])}, 0)};

throwing this error Cannot read property 'reduce' of undefined

i am using in angular 1.5

• javascript
• angularjs
• ecmascript-6
• es6-modules

• 2 That error would have to be happening because you're calling $scope.sum() somewhere with an undefined variable for the list. – Herohtar Commented Nov 8, 2018 at 22:36
• 2 What Herohtar is saying is that the error is independent of the arrow functions, it happens with the old function too. – Tamas Hegedus Commented Nov 8, 2018 at 22:38
• Old function with $scope.sum is working good, now I am trying to ment the old function and trying to do it in Es6...I think what ever i written in es6 syntax there is wrong i hope – mahesh babu Commented Nov 8, 2018 at 22:46
• 3 The syntax of both of those functions is fine. The problem is somewhere else in your code. – Herohtar Commented Nov 8, 2018 at 22:56
• 2 then you must have changed something else, because the two implementations are eqivalent. Plus a more concise version of your code $scope.sum = (list, prop) => list.reduce((a,b) => a+b[prop], 0); – Thomas Commented Nov 8, 2018 at 22:58

1 Answer 1

Your two functions are identical.

const sum1 = function(list, prop){ return list.reduce( function(a, b){ return a + b[prop];}, 0);};

const sum2 = (list,prop) =>  { return list.reduce((a,b) => {return (a+ b[prop])}, 0)};

const list = [{foo:1},{foo:2},{foo:3}]

console.log(sum1(list, 'foo'));
console.log(sum2(list, 'foo'));