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

Similar questions

Having trouble with the removeEventListener OnDestroy not functioning properly in Angular 6 using Javascript?

Unveiling typescript property guards for the unknown data type

Decorating AngularJS' ExceptionHandler with TypeScript is not feasible because a function is not identified as such

Working with ng-model on an array with multiple dimensions

Is there a RxJS equivalent of tap that disregards notification type?

Why is my custom Vuelidate validator not receiving the value from the component where it is being called?

The Next.js build encountered an error - unable to locate function in next/script module

Encountering a new challenge in Angular: The error "InvalidPipeArgument: '' for pipe 'AsyncPipe'

Leveraging a React hook within a Next.js API route

Insert a new key-value pair into a PHP associative array retrieved from a database

After running a yarn build on a TypeScript project using a .projenrc.js file, make sure to include any packaged or additional text files in the lib folder, rather

Tips for successfully importing $lib in SvelteKit without encountering any TypeScript errors

Tips for handling user click events in Angular 2?

Only JSON objects with a boolean value of true will be returned

Is it possible to use square brackets in conjunction with the "this" keyword to access a class property using an expression?

Encountering a DataCorrupted error while decoding a JSON file

Tips for preventing repetition of code in multiple entry points in Rollup

What is the approach to constructing an observable that triggers numerous observables depending on the preceding outcome?

JavaScript problem with setting values in 2D array

Tips for addressing the error "Ensure each child in a list has a distinctive 'key' prop" in a React function using TypeScript