how do you turn this into this?-CodePudding

I have an array:

const arr = [
   { name: "Jeff", id: 1 },
   { name: "Mary", id: 2 },
   { name: "Jeff", id: 3 },
   { name: "Mary", id: 4 },
   { name: "Emile", id: 5 },
];

I want to turn it into this:

const obj = {
    Jeff: [1, 3],
    Mary: [2, 4],
    Emile: [5],
};

I tried using the Array.reduce method, but I can't seem to wrap my head around the logic.

const obj = arr.reduce((acc, info) => {
    acc[info[name]] = .... 
    return acc;
}, {});

I assume it can be done with the reduce method

CodePudding user response：

You are on the right track, you just need to check to see if the array is there.

const arr = [
   { name: "Jeff", id: 1 },
   { name: "Mary", id: 2 },
   { name: "Jeff", id: 3 },
   { name: "Mary", id: 4 },
   { name: "Emile", id: 5 },
];

const result = arr.reduce((acc, { name, id }) => {
  acc[name] = acc[name] || [];  // or if(!acc[name]) acc[name] = [];
  acc[name].push(id);
  return acc;
}, {});

console.log(result);

CodePudding user response：

You can do like this:

const arr = [
  { name: "Jeff", id: 1 },
  { name: "Mary", id: 2 },
  { name: "Jeff", id: 3 },
  { name: "Mary", id: 4 },
  { name: "Emile", id: 5 },
];

const result = arr.reduce(
  (acc, cur) => ((acc[cur.name] || (acc[cur.name] = [])).push(cur.id), acc),
  {}
);

console.log(result);