Answers for "js array reduce with object"

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}

reduce object to array javascript

var arr = [{x:1},{x:2},{x:4}];

arr.reduce(function (a, b) {
  return {x: a.x + b.x}; // returns object with property x
})

// ES6
arr.reduce((a, b) => ({x: a.x + b.x}));

// -> {x: 7}