JavaScript / ES6 -- Replace Some Keys In An Array Of Objects, Given Key Map

I have some (potentially very large) array of objects like this: [ { 'before1' => val, 'same' => val, 'before2' => val }, ... ] I need an efficient way to repla

Solution 1:

Here's a solution using entries:

const arr = [
 {
  'before1': 1,
  'same': 2,
  'before2': 3
 }, {
  'before1': 4,
  'same': 5,
 }, {
  'before1': 6,
  'before2': 7
 }, {
  'same': 8,
  'before2': 9
 },
];

const keyReplacements = {
 'before1': 'after1',
 'same': 'same',    // this is not necessary
 'before2': 'after2'
};

const newArr = arr.map(obj =>
  Object.fromEntries(Object.entries(obj).map(([k, v]) => [keyReplacements[k] || k, v]))
);

console.log(newArr);

Solution 2:

Use ES6 map()

arrayObj = arrayObj.map(item => {
  return {
    value: item.key1,
    key2: item.key2
  };
});