transform an array of objects with map( )

The .map() function will go through the entire array, and on each step of that process it will take the current item that we are looking at and will pass it as a parameter into the function. You can then do whatever you want to that item, and whatever you return from your function will replace what is in that position in the array.

Say for example, with the array you gave in your question, we wanted to remove the name and last_name properties, and combine them into a full_name property. We can do the following:

 let people = [
   {
     id: 1,
     name: 'jhon',
     last_name: 'wilson'
   },
   {
     id: 2,
     name: 'maria',
     last_name: 'anyway'
   },
     id: 3,
     name: 'lastOne',
     last_name: 'example'
   }
];

people = people.map((person) => {
  return {
    id: person.id,
    full_name: `${person.name} ${person.last_name}`
  }
});

After this code runs, our people array would look like this:

[
   {
     id: 1,
     full_name: 'jhon wilson'
   },
   {
     id: 2,
     full_name: 'maria anyway'
   },
     id: 3,
     name: 'lastOne example'
   }
];

You can think of it as doing something very similar to this:

function transformPerson(person) {
  return {
    id: person.id,
    full_name: `${person.name} ${person.last_name}`
  }
}

let newPeople = [];
for (let i = 0; i < people.length; i++) {
  newPeople[i] = transformPerson(people[i])
}

people = newPeople;

Array.map() takes in a function as a parameter, passes each item of the array into the function, and returns an array of the result.

For example, if I wanted to multiply each of the items in the array by 2:

const x = [1, 2, 3, 4, 5]
const y = x.map(v => v * 2) // result: [2, 4, 6, 8, 10]

Note: Array.map does not affect the original array; it creates a new array of the results.

You could change your code to

let people = [{id:1,name:'john',last_name:'wilson'},{id:2,name:'maria',last_name:'anyway'},{id:3,name:'lastOne',last_name:'example'}];

people = people.map((p,i) =>({...p,name: i===1?prompt("New name"):p.name}))

console.log(people);

This will prompt the user only for a new name when i===1. The expression will create a new array that will be stored under the variable name people again. If you wanted people to remain unchanged you could assign the return value of the people.map()-call to a different variable (or constant).