将对象数组减少为键值 map

Question

I have an array of objects. I need to make an object so that I can fetch the name based on an id.

const drinks = [
  { _id: "5fe40ad4d2e6e6de85c46a6c", name: "Americano", __v: 0 },
  { _id: "5fe40ad4d2e6e6de85c46a6d", name: "Latte", __v: 0 },
  { _id: "5fe40ad4d2e6e6de85c46a6e", name: "Flat White", __v: 0 }
];

I tried this which almost works:

console.log(drinks.reduce(
  (accumulator, currentValue) => 
     Object.assign(accumulator, accumulator[currentValue._id] = currentValue.name), {}));

However it outputs:

Object { 
  0: "F", 1: "l", 2: "a", 3: "t", 4: " ", 5: "W", 6: "h", 7: "i", 8: "t", 9: "e",
  5fe40ad4d2e6e6de85c46a6c: "Americano", 
  5fe40ad4d2e6e6de85c46a6d: "Latte", 
  5fe40ad4d2e6e6de85c46a6e: "Flat White" 
}

I need:

Object { 
  5fe40ad4d2e6e6de85c46a6c: "Americano", 
  5fe40ad4d2e6e6de85c46a6d: "Latte", 
  5fe40ad4d2e6e6de85c46a6e: "Flat White"
}

Why is my function also breaking down one of the values into characters?

Answer 1

 const drinks = [{ _id: "5fe40ad4d2e6e6de85c46a6c", name: "Americano", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6d", name: "Latte", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6e", name: "Flat White", __v: 0 }]; const result=drinks.reduce((acc,curr)=>{ acc[curr._id]=curr.name; return acc; },{}) console.log(result)

Answer 2

You can map your array into an array of entries (key / value pairs) which you can then run through Object.fromEntries() to create the final object

 const drinks = [ { _id: "5fe40ad4d2e6e6de85c46a6c", name: "Americano", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6d", name: "Latte", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6e", name: "Flat White", __v: 0 } ] const result = Object.fromEntries(drinks.map(({ _id, name }) => [ _id, name ])) console.log(result)

The longer version would be something like this

const result = drinks.reduce((obj, { _id, name }) => ({
  ...obj, // spread syntax is like `Object.assign()`
  [ _id ]: name // use `_id` as a dynamic object key with value `name`
}), {})

---

The issue with your current code is that the result of...

accumulator[currentValue._id] = currentValue.name

is the value assigned (ie currentValue.name ). When used as an argument in Object.assign() , it is broken down as object entries, thus resulting in what you're seeing with

{ 
  0: "F", 
  1: "l", 
  2: "a", 
  3: "t", 
  4: " ", 
  5: "W", 
  6: "h", 
  7: "i", 
  8: "t", 
  9: "e"
}

Answer 3

Just pass the object { [currentValue._id]: currentValue.name } to assign instead of assignment accumulator[currentValue._id] = currentValue.name

 const drinks = [ { _id: "5fe40ad4d2e6e6de85c46a6c", name: "Americano", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6d", name: "Latte", __v: 0 }, { _id: "5fe40ad4d2e6e6de85c46a6e", name: "Flat White", __v: 0 } ]; console.log(drinks.reduce( (accumulator, currentValue) => Object.assign(accumulator, { [currentValue._id]: currentValue.name }), {}));

Answer 4

This will work

drinks.map(({ _id, name }) => ({
  [_id]: name
}))