Javascript ES6/ES5 find in array and change

You can use findIndex to find the index in the array of the object and replace it as required:

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

var foundIndex = items.findIndex(x => x.id == item.id);
items[foundIndex] = item;

This assumes unique IDs. If your IDs are duplicated (as in your example), it's probably better if you use forEach:

items.forEach((element, index) => {
    if(element.id === item.id) {
        items[index] = item;
    }
});

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)

An other approach is to use splice.

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

N.B : In case you're working with reactive frameworks, it will update the "view", your array "knowing" you've updated it.

Answer :

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

let foundIndex = items.findIndex(element => element.id === item.id)
items.splice(foundIndex, 1, item)

And in case you want to only change a value of an item, you can use find function :

// Retrieve item and assign ref to updatedItem
let updatedItem = items.find((element) => { return element.id === item.id })

// Modify object property
updatedItem.aProp = ds.aProp