Modifying elements in an array using iteration in typescript

Question

Modifying elements in an array using iteration in typescript

I'm trying to figure out how to iterate over an array in TypeScript and modify the iterator if necessary. The TypeScript logic I have so far looks like this:

for (let list_item of list) {
    if (list_item matches condition) {
        modify(list_item);
    }
}

Unfortunately, this approach doesn't seem to work because TypeScript doesn't provide a mutable iterator. Is there a way to achieve this? I've considered enumerating over the array using something like

for (let list_item, index of list) { ... }

, but I'm not sure if that is valid.

You can see an example of the issue I'm facing here: goo.gl/5eDNsD

arrays typescript

Answer 1

Answer №1

Trying to use list_item as a pointer to modify the array won't work. It's simply a value and changing it won't affect the original array. If you want to make changes, you need to directly modify the array using list[idx]. This does mean that the usual for...of loop won't work because it doesn't provide the index.

To achieve what you're after, you can use this syntax instead:

for (let [idx, list_item] of list.entries()) { 
  if list_item meets condition:
    update list[idx]
}

Just to clarify, this concept isn't specific to TypeScript.

Answer 2

Trying to use list_item as a pointer to modify the array won't work. It's simply a value and changing it won't affect the original array. If you want to make changes, you need to directly modify the array using list[idx]. This does mean that the usual for...of loop won't work because it doesn't provide the index.

To achieve what you're after, you can use this syntax instead:

for (let [idx, list_item] of list.entries()) { 
  if list_item meets condition:
    update list[idx]
}

Just to clarify, this concept isn't specific to TypeScript.

Answer 3

Answer №2

When you talk about altering the iterator, are you referring to iterating through the elements and making changes to them based on certain conditions? If so, one way to achieve this is by utilizing the map function.

list = list.map(item => {
    if item meets condition
        modify item and then return it
    }
return item
)

Answer 4

When you talk about altering the iterator, are you referring to iterating through the elements and making changes to them based on certain conditions? If so, one way to achieve this is by utilizing the map function.

list = list.map(item => {
    if item meets condition
        modify item and then return it
    }
return item
)

Answer 5

Answer №3

If you're looking to enhance your code, consider utilizing a library similar to the one found here: https://github.com/labs42io/itiriri#map

Once you have that in place, you can easily implement it like so:

import {transform} from 'itiriri';
transform([1, 2, 3]).map(item => item * 10).toArray(); // yields [10, 20, 30]

Answer 6

If you're looking to enhance your code, consider utilizing a library similar to the one found here: https://github.com/labs42io/itiriri#map

Once you have that in place, you can easily implement it like so:

import {transform} from 'itiriri';
transform([1, 2, 3]).map(item => item * 10).toArray(); // yields [10, 20, 30]

Modifying elements in an array using iteration in typescript

Answer №1

Answer №2

Answer №3

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