There is always going to be a good debate on time vs space, however these days I've found using space is better for the long run.. Mathematics aside let look at a one practical approach to the problem using hashmaps, dictionaries, or associative array's whatever you feel like labeling the simple data structure..

    var marr2 = new Map(arr2.map(e => [e.id, e]));
    arr1.map(obj => marr2.has(obj.id) ? marr2.get(obj.id) : obj);

I like this approach because though you could argue with an array with low numbers you are wasting space because an inline approach like @Tushar approach performs indistinguishably close to this method. However I ran some tests and the graph shows how performant in ms both methods perform from n 0 - 1000. You can decide which method works best for you, for your situation but in my experience users don't care to much about small space but they do care about small speed.

Here is my performance test I ran for source of data

var n = 1000;
var graph = new Array();
for( var x = 0; x < n; x++){
  var arr1s = [...Array(x).keys()];
  var arr2s = arr1s.filter( e => Math.random() > .5);
  var arr1 = arr1s.map(e => {return {id: e, name: 'bill'}});
  var arr2 = arr2s.map(e => {return {id: e, name: 'larry'}});
  // Map 1
  performance.mark('p1s');
  var marr2 = new Map(arr2.map(e => [e.id, e]));
  arr1.map(obj => marr2.has(obj.id) ? marr2.get(obj.id) : obj);
  performance.mark('p1e');
  // Map 2
  performance.mark('p2s');
  arr1.map(obj => arr2.find(o => o.id === obj.id) || obj);
  performance.mark('p2e');
  graph.push({ x: x, r1: performance.measure('HashMap Method', 'p1s', 'p1e').duration, r2: performance.measure('Inner Find', 'p2s','p2e').duration});
}

Just use map like so:

const allItems = [{
    'id': 1,
    'category_id': 1,
    'text': 'old',
  },
  {
    'id': 2,
    'category_id': 1,
    'text': 'old'
  }
];
const newItems = [{
    'id': 1,
    'category_id': 1,
    'text': 'new',
    'more_info': 'abcd'
  },
  {
    'id': 2,
    'category_id': 1,
    'text': 'new',
    'more_info': 'abcd'
  }
];

const replacedItems = allItems.map(e => {
  if (newItems.some(({ id }) => id == e.id)) {
    return newItems.find(({ id }) => id == e.id);
  }
  return e;
});

console.log(replacedItems);

You can use Object.assign() with find() as follows:

const data = [{
    "id": 1,
    "name": "January",
    "abc": "abc",
    "xyz": "xyz"
}, {
    "id": 2,
    "name": "February",
    "abc": "abc",
    "xyz": "xyz"
}];

Object.assign(
    //find the desired object
    data.find(({id,name,abc,xyz}) => id === 2),
    //pass these new values 
    {name:"New Month",abc:"abc123",xyz:"someValue"}
);

console.log( data );

My best approach is:

var item = {...}
var items = [{id:2}, {id:2}, {id:2}];

items[items.findIndex(el => el.id === item.id)] = item;

Reference for findIndex

And in case you don't want to replace with new object, but instead to copy the fields of item, you can use Object.assign:

Object.assign(items[items.findIndex(el => el.id === item.id)], item)

as an alternative with .map():

Object.assign(items, items.map(el => el.id === item.id? item : el))

Functional approach:

Don't modify the array, use a new one, so you don't generate side effects

const updatedItems = items.map(el => el.id === item.id ? item : el)

Note

Properly used, references to objects are not lost, so you could even use the original object reference, instead of creating new ones.

const myArr = [{ id: 1 }, { id: 2 }, { id: 9 }];
const [a, b, c] = myArr;
// modify original reference will change object in the array
a.color = 'green';
console.log(myArr[0].color); // outputs 'green'

This issue usually happens when consuming lists from database and then mapping the list to generate HTML content which will modify the elements of the list, and then we need to update the list and send it back to database as a list.

Good news is, references are kept, so you could organize your code to get advantage of it, and think about a list as an Object with identities for free, which are integers from 0 to length -1. So every time you access any property of your Object, do it as list[i], and you don't lose reference, and original object is changed. Keep in mind that this is useful when your source of truth is only one (the Object created), and your app is always consistently consuming the same Object (not fetching several times from database and assigning it to list along the lifespan of the component).

Bad news is that the architecture is wrong, and you should receive an object by ids (dictionary) if this is what you need, something like

{ 
  1232: { id: 1232, ...},
  asdf234asf: { id: 'asdf234asf', ...},
  ...
}

This way, you don't search in arrays, which is resource consuming. You "just access by key in the object", which is instant and performant.

Use ES6 map()

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

One trick I have used when performance is top priority is to store the data in an object with an array of numeric ids to keep track of everything.

Example similar to yours:

var arr = [
 { id: 1, text: 'aaa' },
 { id: 2, text: 'bbb' },
 { id: 3, text: 'ccc' },
 { id: 78, text: 'zzz' }
];

var lookup = arr.reduce((prev, next) => {
  prev[next.id] = next;
  prev.allIds.push(next.id);
  return prev;
}, { allIds: [] });

Now if you know the id you want to replace you don't need to loop at all

lookup[78] = { id: 78, text: 'new!' };

If you do want to loop through the array use the allIds property

lookup.allIds.forEach(x=> {
  let item = lookup[x];
  item.text = '';
});