 Jad Joubran [X](https://twitter.com/JoubranJad) [GitHub](https://github.com/jadjoubran) [Homepage](https://jadjoubran.io/)
> [!TIP]
> **Celebration:** This web feature is now available in all three major browser engines!
Browsers recently gained a new interoperable method that you can call on Arrays:
[`Array.prototype.with()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/with).
Browser Support
- ' d='M96 183a64 64 0 0 1-23-23L17 64a128 128 0 0 0 111 192l55-96a64 64 0 0 1-87 23Z'/%3E%3Cpath fill='url(%23b)' d='M192 128a64 64 0 0 1-9 32l-55 96A128 128 0 0 0 239 64H128a64 64 0 0 1 64 64Z'/%3E%3Ccircle cx='128' cy='128' r='52' fill='%231a73e8'/%3E%3Cpath fill='url(%23c)' d='M96 73a64 64 0 0 1 32-9h111a128 128 0 0 0-222 0l56 96a64 64 0 0 1 23-87Z'/%3E%3C/svg%3E)
- ' xlink:href='%23A'%3E%3Cstop offset='.76' stop-opacity='0'/%3E%3Cstop offset='.95' stop-opacity='.5'/%3E%3Cstop offset='1'/%3E%3C/radialGradient%3E%3CradialGradient id='F' cx='2523' cy='4680' r='20243' gradientTransform='matrix(-.03715 .99931 -2.12836 -.07913 13579 3530)' xlink:href='%23A'%3E%3Cstop offset='0' stop-color='%2335c1f1'/%3E%3Cstop offset='.11' stop-color='%2334c1ed'/%3E%3Cstop offset='.23' stop-color='%232fc2df'/%3E%3Cstop offset='.31' stop-color='%232bc3d2'/%3E%3Cstop offset='.67' stop-color='%2336c752'/%3E%3C/radialGradient%3E%3CradialGradient id='G' cx='24247' cy='7758' r='9734' gradientTransform='matrix(.28109 .95968 -.78353 .22949 24510 -16292)' xlink:href='%23A'%3E%3Cstop offset='0' stop-color='%2366eb6e'/%3E%3Cstop offset='1' stop-color='%2366eb6e' stop-opacity='0'/%3E%3C/radialGradient%3E%3Cpath id='H' d='M24105 20053a9345 9345 0 01-1053 472 10202 10202 0 01-3590 646c-4732 0-8855-3255-8855-7432 0-1175 680-2193 1643-2729-4280 180-5380 4640-5380 7253 0 7387 6810 8137 8276 8137 791 0 1984-230 2704-456l130-44a12834 12834 0 006660-5282c220-350-168-757-535-565z'/%3E%3Cpath id='I' d='M11571 25141a7913 7913 0 01-2273-2137 8145 8145 0 01-1514-4740 8093 8093 0 013093-6395 8082 8082 0 011373-859c312-148 846-414 1554-404a3236 3236 0 012569 1297 3184 3184 0 01636 1866c0-21 2446-7960-8005-7960-4390 0-8004 4166-8004 7820 0 2319 538 4170 1212 5604a12833 12833 0 007684 6757 12795 12795 0 003908 610c1414 0 2774-233 4045-656a7575 7575 0 01-6278-803z'/%3E%3Cpath id='J' d='M16231 15886c-80 105-330 250-330 566 0 260 170 512 472 723 1438 1003 4149 868 4156 868a5954 5954 0 003027-839 6147 6147 0 001133-850 6180 6180 0 001910-4437c26-2242-796-3732-1133-4392-2120-4141-6694-6525-11668-6525-7011 0-12703 5635-12798 12620 47-3654 3679-6605 7996-6605 350 0 2346 34 4200 1007 1634 858 2490 1894 3086 2921 618 1067 728 2415 728 2952s-271 1333-780 1990z'/%3E%3Cuse fill='url(%23B)' xlink:href='%23H'/%3E%3Cuse fill='url(%23D)' opacity='.35' xlink:href='%23H'/%3E%3Cuse fill='url(%23C)' xlink:href='%23I'/%3E%3Cuse fill='url(%23E)' opacity='.4' xlink:href='%23I'/%3E%3Cuse fill='url(%23F)' xlink:href='%23J'/%3E%3Cuse fill='url(%23G)' xlink:href='%23J'/%3E%3C/svg%3E)
- ' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.2' stop-color='%239059ff' stop-opacity='0'/%3E%3Cstop offset='.3' stop-color='%238c4ff3' stop-opacity='.1'/%3E%3Cstop offset='.8' stop-color='%237716a8' stop-opacity='.5'/%3E%3Cstop offset='1' stop-color='%236e008b' stop-opacity='.6'/%3E%3C/radialGradient%3E%3CradialGradient id='ff-g' cx='239.1' cy='34.6' r='171.6' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='0' stop-color='%23ffe226'/%3E%3Cstop offset='.1' stop-color='%23ffdb27'/%3E%3Cstop offset='.3' stop-color='%23ffc82a'/%3E%3Cstop offset='.5' stop-color='%23ffa930'/%3E%3Cstop offset='.7' stop-color='%23ff7e37'/%3E%3Cstop offset='.8' stop-color='%23ff7139'/%3E%3C/radialGradient%3E%3CradialGradient id='ff-h' cx='374' cy='-74.3' r='732.2' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.1' stop-color='%23fff44f'/%3E%3Cstop offset='.5' stop-color='%23ff980e'/%3E%3Cstop offset='.6' stop-color='%23ff5634'/%3E%3Cstop offset='.7' stop-color='%23ff3647'/%3E%3Cstop offset='.9' stop-color='%23e31587'/%3E%3C/radialGradient%3E%3CradialGradient id='ff-i' cx='304.6' cy='7.1' r='536.4' gradientTransform='rotate(84 303 4)' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='0' stop-color='%23fff44f'/%3E%3Cstop offset='.1' stop-color='%23ffe847'/%3E%3Cstop offset='.2' stop-color='%23ffc830'/%3E%3Cstop offset='.3' stop-color='%23ff980e'/%3E%3Cstop offset='.4' stop-color='%23ff8b16'/%3E%3Cstop offset='.5' stop-color='%23ff672a'/%3E%3Cstop offset='.6' stop-color='%23ff3647'/%3E%3Cstop offset='.7' stop-color='%23e31587'/%3E%3C/radialGradient%3E%3CradialGradient id='ff-j' cx='235' cy='98.1' r='457.1' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.1' stop-color='%23fff44f'/%3E%3Cstop offset='.5' stop-color='%23ff980e'/%3E%3Cstop offset='.6' stop-color='%23ff5634'/%3E%3Cstop offset='.7' stop-color='%23ff3647'/%3E%3Cstop offset='.9' stop-color='%23e31587'/%3E%3C/radialGradient%3E%3CradialGradient id='ff-k' cx='355.7' cy='124.9' r='500.3' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.1' stop-color='%23fff44f'/%3E%3Cstop offset='.2' stop-color='%23ffe141'/%3E%3Cstop offset='.5' stop-color='%23ffaf1e'/%3E%3Cstop offset='.6' stop-color='%23ff980e'/%3E%3C/radialGradient%3E%3ClinearGradient id='ff-a' x1='446.9' y1='76.8' x2='47.9' y2='461.8' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.1' stop-color='%23fff44f'/%3E%3Cstop offset='.1' stop-color='%23ffe847'/%3E%3Cstop offset='.2' stop-color='%23ffc830'/%3E%3Cstop offset='.4' stop-color='%23ff980e'/%3E%3Cstop offset='.4' stop-color='%23ff8b16'/%3E%3Cstop offset='.5' stop-color='%23ff672a'/%3E%3Cstop offset='.5' stop-color='%23ff3647'/%3E%3Cstop offset='.7' stop-color='%23e31587'/%3E%3C/linearGradient%3E%3ClinearGradient id='ff-l' x1='442.1' y1='74.8' x2='102.6' y2='414.3' gradientUnits='userSpaceOnUse'%3E%3Cstop offset='.2' stop-color='%23fff44f' stop-opacity='.8'/%3E%3Cstop offset='.3' stop-color='%23fff44f' stop-opacity='.6'/%3E%3Cstop offset='.5' stop-color='%23fff44f' stop-opacity='.2'/%3E%3Cstop offset='.6' stop-color='%23fff44f' stop-opacity='0'/%3E%3C/linearGradient%3E%3C/defs%3E%3Cpath d='M479 166c-11-25-32-52-49-60a249 249 0 0 1 25 73c-27-68-73-95-111-155a255 255 0 0 1-8-14 44 44 0 0 1-4-9 1 1 0 0 0 0-1 1 1 0 0 0-1 0c-60 35-81 101-83 134a120 120 0 0 0-66 25 71 71 0 0 0-6-5 111 111 0 0 1-1-58c-25 11-44 29-58 44-9-12-9-52-8-60l-8 4a175 175 0 0 0-24 21 210 210 0 0 0-22 26 203 203 0 0 0-32 73l-1 2-2 15a229 229 0 0 0-4 34v1a240 240 0 0 0 477 40l1-9c5-41 0-84-15-121zM202 355l3 1-3-1zm55-145zm198-31z' fill='url(%23ff-a)'/%3E%3Cpath d='M479 166c-11-25-32-52-49-60 14 26 22 53 25 72v1a207 207 0 0 1-206 279c-113-3-212-87-231-197-3-17 0-26 2-40-2 11-3 14-4 34v1a240 240 0 0 0 477 40l1-9c5-41 0-84-15-121z' fill='url(%23ff-b)'/%3E%3Cpath d='M479 166c-11-25-32-52-49-60 14 26 22 53 25 72v1a207 207 0 0 1-206 279c-113-3-212-87-231-197-3-17 0-26 2-40-2 11-3 14-4 34v1a240 240 0 0 0 477 40l1-9c5-41 0-84-15-121z' fill='url(%23ff-c)'/%3E%3Cpath d='m362 195 1 1a130 130 0 0 0-22-29C266 92 322 5 331 0c-60 35-81 101-83 134l9-1c45 0 84 25 105 62z' fill='url(%23ff-d)'/%3E%3Cpath d='M257 210c-1 6-22 26-29 26-68 0-80 41-80 41 3 35 28 64 57 79l4 2 7 3a107 107 0 0 0 31 6c120 6 143-143 57-186 22-4 45 5 58 14-21-37-60-62-105-62l-9 1a120 120 0 0 0-66 25l17 16c16 16 58 33 58 35z' fill='url(%23ff-e)'/%3E%3Cpath d='M257 210c-1 6-22 26-29 26-68 0-80 41-80 41 3 35 28 64 57 79l4 2 7 3a107 107 0 0 0 31 6c120 6 143-143 57-186 22-4 45 5 58 14-21-37-60-62-105-62l-9 1a120 120 0 0 0-66 25l17 16c16 16 58 33 58 35z' fill='url(%23ff-f)'/%3E%3Cpath d='m171 151 5 3a111 111 0 0 1-1-58c-25 11-44 29-58 44 1 0 36 0 54 11z' fill='url(%23ff-g)'/%3E%3Cpath d='M18 261a242 242 0 0 0 231 197 207 207 0 0 0 206-279c8 56-20 110-64 146-86 71-169 43-186 31l-3-1c-50-24-71-70-67-110-42 0-57-35-57-35s38-28 89-4c46 22 90 4 90 4 0-2-42-19-58-35l-17-16a71 71 0 0 0-6-5l-5-3c-18-11-52-11-54-11-9-12-9-51-8-60l-8 4a175 175 0 0 0-24 21 210 210 0 0 0-22 26 203 203 0 0 0-32 73c0 1-9 38-5 57z' fill='url(%23ff-h)'/%3E%3Cpath d='M341 167a130 130 0 0 1 22 29 46 46 0 0 1 4 3c55 50 26 121 24 126 44-36 72-90 64-146-27-68-73-95-111-155a255 255 0 0 1-8-14 44 44 0 0 1-4-9 1 1 0 0 0 0-1 1 1 0 0 0-1 0c-9 5-65 92 10 167z' fill='url(%23ff-i)'/%3E%3Cpath d='M367 199a46 46 0 0 0-4-3l-1-1c-13-9-36-18-58-15 86 44 63 193-57 187a107 107 0 0 1-31-6 131 131 0 0 1-11-5c17 12 99 39 186-31 2-5 31-76-24-126z' fill='url(%23ff-j)'/%3E%3Cpath d='M148 277s12-41 80-41c7 0 28-20 29-26s-44 18-90-4c-51-24-89 4-89 4s15 35 57 35c-4 40 16 85 67 110l3 1c-29-15-54-44-57-79z' fill='url(%23ff-k)'/%3E%3Cpath d='M479 166c-11-25-32-52-49-60a249 249 0 0 1 25 73c-27-68-73-95-111-155a255 255 0 0 1-8-14 44 44 0 0 1-4-9 1 1 0 0 0 0-1 1 1 0 0 0-1 0c-60 35-81 101-83 134l9-1c45 0 84 25 105 62-13-9-36-18-58-14 86 43 63 192-57 186a107 107 0 0 1-31-6 131 131 0 0 1-11-5l-3-1 3 1c-29-15-54-44-57-79 0 0 12-41 80-41 7 0 28-20 29-26 0-2-42-19-58-35l-17-16a71 71 0 0 0-6-5 111 111 0 0 1-1-58c-25 11-44 29-58 44-9-12-9-52-8-60l-8 4a175 175 0 0 0-24 21 210 210 0 0 0-22 26 203 203 0 0 0-32 73l-1 2-2 15a279 279 0 0 0-4 34v1a240 240 0 0 0 477 40l1-9c5-41 0-84-15-121zm-24 13z' fill='url(%23ff-l)'/%3E%3C/svg%3E)
- ' xlink:href='%23s-b'%3E%3Cstop offset='0' stop-color='%2324a5f3' stop-opacity='0' /%3E%3Cstop offset='1' stop-color='%231e8ceb' /%3E%3C/radialGradient%3E%3CradialGradient id='s-j' cx='109.3' cy='13.8' r='93.1' gradientTransform='matrix(-.02 1.1 -1.04 -.02 137 -115)' xlink:href='%23s-b'%3E%3Cstop offset='0' stop-opacity='0' /%3E%3Cstop offset='1' stop-color='%235488d6' stop-opacity='0' /%3E%3Cstop offset='1' stop-color='%235d96eb' /%3E%3C/radialGradient%3E%3C/defs%3E%3Crect width='220' height='220' x='22' y='-107' fill='url(%23s-a)' ry='49' transform='matrix(.57 0 0 .57 187 256)' /%3E%3Cg transform='translate(194 190)'%3E%3Ccircle cx='67.8' cy='67.7' fill='url(%23s-c)' paint-order='stroke fill markers' r='54' /%3E%3Ccircle cx='-69.9' cy='69.3' fill='url(%23s-i)' transform='translate(138 -2)' r='54' /%3E%3C/g%3E%3Cellipse cx='120' cy='14.2' fill='url(%23s-j)' rx='93.1' ry='93.7' transform='matrix(.58 0 0 .58 192 250)' /%3E%3Cg transform='matrix(.58 0 0 .57 197 182)'%3E%3Cpath fill='%23cac7c8' d='M46 192h1l72-48-7-9-66 57Z' /%3E%3Cpath fill='%23fbfffc' d='M46 191v1l66-57-7-9-59 65Z' /%3E%3Cpath fill='url(%23s-d)' d='m119 144-7-9 66-57-59 66Z' /%3E%3Cpath fill='%23fb645c' d='m105 126 7 9 66-57-1-1-72 49Z' /%3E%3C/g%3E%3Cpath stroke='%23fff' stroke-linecap='round' stroke-miterlimit='1' stroke-width='1.3' d='m287 278 3-2m-12-17 8-2m-8-3h4m-4-13 8 2m-8 3h4m-1-13 7 3m-4-11 7 4m-2-11 6 6m0-12 6 7m1-11 4 6m4-10 3 7m5-9 2 7m15-7-1 7m10-5-3 7m11-4-4 7m11-2-5 6m16 7-7 4m10 4-7 3m10 6-8 1m8 16-8-2m5 10-7-3m4 11-7-4m2 11-6-5m0 11-5-6m-2 11-4-7m-4 11-3-8m-6 10-1-8m-16 8 2-8m-10 5 3-7m-11 4 4-7m-11 2 5-6m-8 3 3-3m4 8 2-3m5 8 2-4m6 7 1-4m8 5v-4m8 4v-4m9 3-1-4m9 1-2-4m9 0-2-4m9-2-3-3m8-4-3-2m8-5-4-2m7-6-4-1m5-8h-4m4-8h-4m3-9-4 1m1-9-4 2m-1-9-3 2m-2-9-3 3m-4-8-2 3m-5-8-2 4m-6-6-1 3m-8-5v4m-8-4v4m-9-2 1 3m-9 0 2 3m-9 1 2 3m-9 2 3 3m-8 4 3 2m-8 5 4 2m-7 6 4 1m-4 25 4-1m-2 5 7-3m-6 7 4-2m-2 6 7-4m-13-21h8m41-41v-8m0 99v-8m49-42h-8' transform='translate(-65 8)' /%3E%3C/svg%3E)
[Source](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/with)
This article explores how this method works and how to use it to update an array
without mutating the original array.
## Intro to `Array.prototype.with(index, value)`
The `Array.prototype.with(index, value)` method returns a copy of the array it's
called on with the `index` set to the new `value` you provide.
The following example shows an array of ages. You'd like to create a new copy of
the array while changing the second age from 15 to 16:
```javascript
const ages = [10, 15, 20, 25];
const newAges = ages.with(1, 16);
console.log(newAges); // [10, 16, 20, 25]
console.log(ages); // [10, 15, 20, 25] (unchanged)
```
Breaking down the code:: `ages.with(...)` returns a copy of the `ages` variable
without modifying the original array. `ages.with(1, ...)` replaces the second item
(`index = 1`). `ages.with(1, 16)` assigns the second item to `16`.
This is how you were able to create a new copy of the array with a modification.
This is pretty useful when you want to make sure that the original array remains
unchanged, and this article covers some of the use cases for this. But, for now,
take a look at what would have happened had you used the bracket notation:
```javascript
const ages = [10, 15, 20, 25];
const newAges = ages;
newAges[1] = 16;
console.log(newAges); // [10, 16, 20, 25]
console.log(ages); // [10, 16, 20, 25] (Also changed 🙁)
```
As you can see, the `ages` variable was also modified in this example. That's
because when you assign `ages = newAges`, JavaScript does not copy the array but
rather creates a reference to the other array. So, any change in one will also
affect the other one as they are both pointing to the same array.
## Array.prototype.with() and immutability
Immutability is at the heart of many frontend libraries and frameworks, to name
a few: React (and redux), and Vue
Also, other libraries and frameworks don't necessarily require immutability but
encourage it for better performance: Angular and Lit
So, developers often had to use other methods that returned copies of arrays
which sacrificed code readability:
```javascript
const ages = [10, 15, 20, 25];
const newAges = ages.map((age, index) => {
if (index === 1) {
return 16;
}
return age;
});
console.log(newAges); // [10, 16, 20, 25]
console.log(ages); // [10, 15, 20, 25] (Remains unchanged)
```
Here's an example Codepen of how `.with()` can be used in React in combination
with useState to immutably update an array of items:
Since the `.with()` method returns a copy of the array, you can chain multiple
`.with()` calls or even other array methods. The following example demonstrates
incrementing the second and third ages from the array:
```javascript
const ages = [10, 15, 20, 25];
const newAges = ages.with(1, ages[1] + 1).with(2, ages[2] + 1)
console.log(newAges); // [10, 16, 21, 25]
console.log(ages); // [10, 15, 20, 25] (unchanged)
```
## Other new immutable methods
Three other methods recently became interoperable:
- [`Array.prototype.toReversed()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/toReversed) which reverses the array without mutating the original array.
- [`Array.prototype.toSorted()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/toSorted) which sorts the array without mutating the original array.
- [`Array.prototype.toSpliced()`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/toSpliced) which works like `.splice()` but without mutating the original array.
These three methods are, according to MDN, the copying version of their
counterparts. These methods can also be used where immutability is expected or
preferred.
In conclusion, immutable updates can be achieved more easily in
JavaScript with one of the four methods presented in this article. Specifically,
the `.with()` method makes it easier to update a single element of the array
without mutating the original array.