Javascript: mapping over an array and sorting the return array depending on a lookup object

Question

Hi I would like to map over an array and sort it depending on an lookup object.

const obj = {
  "email": {position: 1, name: "email"},
  "firstname": {position: 2, name: "firstname"},
  "lastname": {position: 3, name: "lastname"}
}

const arr = ["lastname", "email", "firstname"];

expected output: ["email", "firstname", "lastname"];

I know that I must use the map function in order to return a new array. I can get an new array with the full or object or retrieving only a array with all names or position properties. But I cannot figure out how to sort them.

Thanks for your help

IT goldman · Accepted Answer · 2022-11-04 18:43:06Z

5

Array.sort function accepts a callback (sorter) function that will return comparison of any two items in array. So just need to compare their position (of 2 items in array). This is done by substracting them to get a positive/0/negative result.

const obj = {
  "email": {position: 1, name: "email"},
  "firstname": {position: 2, name: "firstname"},
  "lastname": {position: 3, name: "lastname"}
}

const arr = ["lastname", "email", "firstname"];

// expected output: ["email", "firstname", "lastname"];
arr.sort(function(a,b) {
  return obj[a].position - obj[b].position
})

console.log(arr)

answered Nov 4, 2022 at 18:43

IT goldman

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