Iterate an array of objects

byMR

July 8, 2022

I have an array of objects.

myArray = [{a:1,b:1,c:1,d:1},{a:2,b:2,c:2,d:2},{a:3,b:3,c:3,d:3},{a:4,b:4,c:4,d:4}]

I want to create a new dictionary from it:
newDict = {a:[1,2,3,4],c:[1,2,3,4]}

I’m totally new to Javascript and Node.js
Any kind of help is highly appreciated.
Thanks in advance.

>Solution :

Alternatively you can also do it in a for loop, in case you are unfamiliar with the reduce method.

const myArray = [{a:1,b:1,c:1,d:1},{a:2,b:2,c:2,d:2},{a:3,b:3,c:3,d:3},{a:4,b:4,c:4,d:4}]

const wantedProperties = ['a', 'b', 'd']

const mydict = {}
for (const item of myArray) {
  for (const [key, value] of Object.entries(item)) {
    if (wantedProperties.includes(key)) {
     mydict[key] = (mydict[key] || []).concat(value)
    }
  }
}

console.log(mydict)