JavaScript / ES6 -- Replace some keys in an array of objects, given key map

Question

I have some (potentially very large) array of objects like this:

[
 {
  'before1' => val,
  'same' => val,
  'before2' => val
 },
  ...
]

I need an efficient way to replace only some of the keys in the map (i.e. deleting keys won't work for me), and I have a map like this:

keyReplacements = {
 'before1' => 'after1',
 'same' => 'same',
 'before2' => 'after2'
}

I know the same => same is not necessary in the map, but it's helpful to include as a full translation schema.

Given this key mapping, what's an efficient method to replace my given array of objects with the following result?

[
 {
  'after1' => val,
  'same' => val,
  'after2' => val
 },
  ...
]

I've tried the following:

    static replaceObjectKeys(objectToReplace, keyMap) {
        objectToReplace.map(o =>
        Object.keys(o).map((key) => ({ [keyMap[key] || key]: o[key] })
        ).reduce((objectToReplace, b) => Object.assign({}, objectToReplace, b)))

        return objectToReplace
    }

But it just returns me the same object with nothing replaced

const newObject = this.replaceObjectKeys(oldObject, keyMap)
console.log("new obj: ", newObject) // this is the same as oldObject
return newObject

Does this answer your question? [JavaScript: Object Rename Key](https://stackoverflow.com/questions/4647817/javascript-object-rename-key) — gbalduzzi, Aug 18 '20 at 08:49
Edited the OP with an attempt I had earlier -- I could do this in PHP trivially but I'm not very familiar with Javascript/ES6 so I'm having a difficult time debugging the syntax and functions — ShaneOH, Aug 18 '20 at 08:51

Hao Wu · Accepted Answer · 2020-08-18T08:56:37.470

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);

score 0 · Answer 2 · answered Aug 18 '20 at 08:49

0

Use ES6 map()

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

answered Aug 18 '20 at 08:49

Mindaugas Kurlys

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JavaScript / ES6 -- Replace some keys in an array of objects, given key map

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