Answers for "reducer in javascript from array objects"

javascript reduce array of objects

var objs = [
  {name: "Peter", age: 35},
  {name: "John", age: 27},
  {name: "Jake", age: 28}
];

objs.reduce(function(accumulator, currentValue) {
  return accumulator + currentValue.age;
}, 0); // 35 + 27 + 28 = 90

forming an object with reduce

const FRUITS = ["banana", "apple", "orange", "banana", "orange",
"apple", "apple", "orange", "orange", "banana", "orange", "banana"];

const total = FRUITS.reduce((map, fruit) => ({
  ...map,
  [fruit]: (map[fruit] || 0) + 1,
}), {});
console.log(total); // { banana: 4, apple: 3, orange: 5}