Explained in detail at this link, TypeScript introduces a foreach loop:
let someArray = [9, 2, 5];
for (let item of someArray) {
console.log(item); // 9,2,5
}
However, is there a way to access the index/key? I was thinking something along the lines of:
for (let key = 0; let item of someArray) { ... }
.forEach already has the capability:
const myArray = [9, 2, 5];
myArray.forEach((val, idx) => {
console.log(idx); // 0, 1, 2
console.log(val); // 9, 2, 5
});
If you prefer the features of for...of, you can use map on the array to retrieve the index and value:
for (const { idx, val } of myArray.map((val, idx) => ({ idx, val }))) {
console.log(idx); // 0, 1, 2
console.log(val); // 9, 2, 5
}
If this seems lengthy, consider encapsulating it in a reusable function:
function extractEntries<T>(arr: T[]) {
return arr.map((val, idx) => [idx, val] as const);
}
for (const [idx, val] of extractEntries(myArray)) {
// ..etc..
}
Iterable Approach
This approach is functional for ES3 or ES5 if compiled with the --downlevelIteration flag.
function* extractEntries<T>(values: T[] | IterableIterator<T>) {
let idx = 0;
for (const val of values) {
yield [idx, val] as const;
idx++;
}
}
Array.prototype.entries() - For ES6+
In ES6+ environments, utilize the .entries() method detailed in this post.
Check out: Array.prototype.entries()
for (const [index, item] of someArray.entries()) { ... }
To implement this in TypeScript, targeting ES2015 is necessary since it relies on runtime support for iterators. For compatibility with ES5 runtimes, tools like Babel can be used to make the code compatible with ES5 environments.
Bringing back the traditional ways of JavaScript to save the day (for those not well-versed/intrigued by functional programming)
for (let i = 0; i < someArray.length ; i++) {
let item = someArray[i];
}
To access the index when working with collections, you can utilize the for..in operator in TypeScript.
var numbers = [7, 8, 9];
for (let index in numbers) {
console.log(index + ': ' + numbers[index]);
}
Output:
0: 7
1: 8
2: 9
Check out this demo
Or you could opt for a more traditional approach:
const numbers = [7, 3, 6];
let index = 0;
for (const num of numbers) {
console.log(num); // Outputs: 7, 3, 6
index++;
}
Let me walk you through the code that is currently working: <input [formControl]="search" [typeahead]="suggestions" typeaheadOptionField="name" (typeaheadOnSelect)="onSelectedDriver($event)&qu ...
Here is an example of code snippet: import * as React from 'react'; co ...
I am a beginner with Angular2 and I am currently working on creating a reactive form, specifically an interactive date input field. Here is my HTML code: <div class="date ui-input"> <input type="text" name="dateD" [ngModel]="model.date | dat ...
I have a dynamic page where I need to click on a button. I tried the code below, but it is not working and not showing any alert. However, if we use the same code in the browser console, it executes and shows an alert. Can someone please suggest how to r ...
Whenever I attempt to compile the project for production, an error pops up: There is a problem resolving all parameters for EmployeeComponent in C:/.../src/app/employee/employee.component.ts: (?, ?, ?). Oddly enough, when I run the application, every ...
Currently, I am working on an Angular 8 application that consists of two components with a child-parent relationship. It came to my notice that even after removing an item from the child component, the item remains visible in the parent component's li ...
After creating a new Angular application, I am encountering the issue of getting the error message "X is not declared in any Angular module" on every component, including the automatically generated AppComponent. Despite having the latest version of the An ...
I'm currently learning angularjs 2 and I'm eager to create my first application using the framework. Following the guidelines on their official website, I proceeded with all the steps outlined in this link. In step 6, I am required to run the com ...
Is it possible to bind the display style of a table row using knockout.js with a viewmodel property? I need to utilize this binding in order to toggle the visibility of the table row based on other properties within my viewmodel. Here is an example of HTM ...
I'm having trouble extending Express' Request object to access req.user, and I'm encountering an overload error. I've attempted a couple of solutions, but none of them seem to work for me. EDIT: I am currently using Passport.js and JWT ...
Using the documentSnapshot function in Firestore to verify the existence of a document. The function is executed in a loop up to a value of 5. However, even though the function runs 5 times, the value of 'i' always reflects the last value. The ...
Every time I attempt to run any code, I encounter the following error message: No HTTP methods exported in 'file path'. Export a named export for each HTTP method. Below is the content of my route.ts file: import type { NextApiRequest, NextApi ...
The objective is to prevent developers from declaring or accessing fields that the object does not possess. This also involves accurately defining a deeply nested object or schema. const theme: iTheme = { palletes: { primary: { main: "white", ...
Currently, I am fetching data from a service within the app component and passing it down to a child component using @Input. Oddly enough, when I log the data in ngOnInit, it appears correctly in the child component. However, when I try to assign it to a v ...
My interface contains a nested object: export interface Person { PersonWrapper: { name: string; address: string email?: string; } } When attempting to create an object from this interface, it appears that name is not mandat ...
Our application employs express along with TypeScript. While exploring their type definitions, I stumbled upon the following snippet and I'm curious about its meaning: export interface IRouter extends RequestHandler { all: IRouterMatcher<this& ...
Looking to define an interface for a team object: export interface Team{ memberUid?: { mail: string name: string photoURL: string } startDate: Timestamp endDate: Timestamp agenda: Array<{ date: Date | Timestamp title: strin ...
Reflecting on ways to incorporate members in a component that can be accessed from the template but not from a parent component sparked my curiosity. In exploring TypeScript visibility in Angular 2, I encountered discussions about "public" and "private" d ...
I'm looking to add a new key value pair to an existing object without declaring it inside the initial object declaration. I attempted the code below, but encountered the following error: Property 'specialty' does not exist on type saveFor ...
After clicking the MultipleComponent button, all logs in the function return null. However, when clicked a second time, it returns the previous values. Is there a way to retrieve the current status in each log within the map function? Concerning the useEf ...