如何从字符串数组创建对象映射？

Question

i am stumbling onto something that should be easy, yet i can't seem to be able to do it.

i have an array of string, and i want to map over it to create an object like so :

const monthesList = ['january', 'february', 'march', 'april', 'may']

const myState = monthesList.map(month => (
    month: {selected: false, year: 2022}
    )
  )

what i want is to get the following object :

myState ={
  january:{ 
    selected: false,
    year: 2022
  },
  february:{ 
    selected: false,
    year: 2022
  },
  march:{ 
    selected: false,
    year: 2022
  },
  april:{ 
    selected: false,
    year: 2022
  },
  may:{ 
    selected: false,
    year: 2022
  },
}

Edit: i just found the way :

const myState = monthesList.map(month => (
    {[month] : {
      selected: false,
      year: 2022
    }}
    )
  )

just need to make an object out of it, shouldn't be too hard

Answer 1

The .map() method returns an array, but the output that you're after is an object. You need something that can convert an array of key-value pairs (ie: [key, value] ) to an object. For this, we have the Object.fromEntries() method that takes an array of key-value pairs, and from it, constructs an object like so:

 const monthesList = ['january', 'february', 'march', 'april', 'may']; const myState = Object.fromEntries(monthesList.map(month => [ month, {selected: false, year: 2022} ])); console.log(myState);

Answer 2

You can use map to generate an array of arrays with the values in each internal array being the month name and object; then use Object.fromEntries to convert that into your desired object:

 const monthesList = ['january', 'february', 'march', 'april', 'may'] const myState = Object.fromEntries( monthesList.map(m => [m, {selected: false, year: 2022}]) ) console.log(myState)

Answer 3

map will only return an array. Your expected output is an object. There's no need to over-complicate things - use a simple loop instead.

 const list = ['january', 'february', 'march', 'april', 'may']; const myState = {}; for (const month of list) { myState[month] = { selected: false, year: 2022 }; } console.log(myState);