What is the best way to sum arrays using ECMASCRIPT 6 Generator/Functions

Question

Is there a better way instead of adding values of arrays up using a generator function as closure?

var sumArrays = function(){
  var sum = 0;
  return function*(){
    while(true){
      var array = yield sum;
      if(array.__proto__.constructor === Array){
        sum += array.reduce(function(val,val2){ return val+val2; });
      }
      else sum=0;
    }
  };
};

var gen = sumArrays();
// is this step required to make a generator or could it be done at least differently to spare yourself from doing this step?
gen = gen();

// sum some values of arrays up
console.log('sum: ',gen.next()); // Object { value=0,  done=false}
console.log('sum: ',gen.next([1,2,3,4])); // Object { value=10,  done=false}
console.log('sum: ',gen.next([6,7])); // Object { value=23,  done=false}

// reset values
console.log('sum: ',gen.next(false)); // Object { value=0,  done=false}
console.log('sum: ',gen.next([5])); // Object { value=5,  done=false}

Answer 1

This doesn't seem to be a problem generators are supposed to solve, so I would not use a generator here.

Directly using reduce (ES5) seems to be more appropriate:

let sum = [1,2,3,4].reduce((sum, x) => sum + x);

As a function:

function sum(arr) {
  return arr.reduce((sum, x) => sum + x);
}

If you really want to sum multiple arrays across multiple function calls, then return a normal function:

function getArraySummation() {
  let total = 0;
  let reducer = (sum, x) => sum + x;
  return arr => total + arr.reduce(reducer);
}

let sum = getArraySummation();
console.log('sum:', sum([1,2,3])); // sum: 6
console.log('sum:', sum([4,5,6])); // sum: 15

Keep it simple.