Enhance your TypeScript arrays using custom object equality functions

Question

Enhance your TypeScript arrays using custom object equality functions

I am looking to utilize array functions such as contains and unique, but I want them to compare equality using my custom equals function.

For instance:

let arr = [{id:1,..//some more},{id:2,..//some more},{id:3,..//some more}]

I need the following code to return true by using an equals function that checks only the id property:

arr.contains({id:1,....}).

I have attempted to search for a solution but haven't been successful.

How can I achieve this? And in general, how can I implement my own equal function in TypeScript (similar to the equals function in Java).

javascript arrays typescript

Answer 1

Answer №1

When it comes to array functions like includes or indexOf, the equality check cannot be altered. However, there are other array functions that allow you to implement a callback instead:

find - Identifies the first entry in the array that satisfies your callback function's condition
findIndex - Determines the position of the first entry in the array for which your callback returns true
some - Iterates through the array, executing your callback until a truthy value is returned (at which point, some stops and returns true); if no truthy value is returned by the callback, some will return false.
every - Goes through each element of the array, invoking your callback until a falsy value is returned (in this case, every halts and returns false); if the callback never produces a falsy value, every returns true.

All these functions have detailed explanations with links available on the MDN array page.

For instance, using custom equality to find if an array contains certain elements can be achieved with the some function:

const a = [
  {id: 1},
  {id: 2},
  {id: 3}
];
console.log("Has 1? " + a.some(e => e.id == 1));
console.log("Has 4? " + a.some(e => e.id == 4));

Answer 2

When it comes to array functions like includes or indexOf, the equality check cannot be altered. However, there are other array functions that allow you to implement a callback instead:

find - Identifies the first entry in the array that satisfies your callback function's condition
findIndex - Determines the position of the first entry in the array for which your callback returns true
some - Iterates through the array, executing your callback until a truthy value is returned (at which point, some stops and returns true); if no truthy value is returned by the callback, some will return false.
every - Goes through each element of the array, invoking your callback until a falsy value is returned (in this case, every halts and returns false); if the callback never produces a falsy value, every returns true.

All these functions have detailed explanations with links available on the MDN array page.

For instance, using custom equality to find if an array contains certain elements can be achieved with the some function:

const a = [
  {id: 1},
  {id: 2},
  {id: 3}
];
console.log("Has 1? " + a.some(e => e.id == 1));
console.log("Has 4? " + a.some(e => e.id == 4));

Answer 3

Answer №2

You have the option to utilize the find method and verify that the returned value is not undefined.

For instance:

let myList = [{id: 1, value: 'Apple'}, {id: 2, value: 'Banana'}];
const checkIdOne = item => item.id === 1;
const hasIdOne = myList.find(checkIdOne) !== undefined;

Answer 4

You have the option to utilize the find method and verify that the returned value is not undefined.

For instance:

let myList = [{id: 1, value: 'Apple'}, {id: 2, value: 'Banana'}];
const checkIdOne = item => item.id === 1;
const hasIdOne = myList.find(checkIdOne) !== undefined;

Enhance your TypeScript arrays using custom object equality functions

Answer №1

Answer №2

Similar questions

Mapping a response object to a Type interface with multiple Type Interfaces in Angular 7: A step-by-step guide

Expanding interfaces dynamically in Typescript

Can the getState() method be utilized within a reducer function?

Interact with AJAX form to dynamically display result data in the intended DIV

Angular 14: A collection and schematic must be provided for execution to proceed with the process

Can one utilize generic parameter value within a conditional type result field in Typescript?

The optimal method for loading CSS and Javascript from an ajax response within a JavaScript function - Ensuring cross-browser compatibility

Watchable: Yield the outcome of a Promise as long as watching continues

Ways to set the className prop for all components automatically without having to specify it repeatedly

Time picker in Bootstrap - Ensuring end time is not earlier than start time validation

Looking to adjust the HSL of individual colors on a JavaScript canvas, similar to editing in Photoshop?

Utilizing Angular 7, Ngrx, and Rxjs 6 to efficiently share state data among lazily loaded modules

Tips on dividing and recycling mongodb connection in Node.js

Issues with changing background colors using Jquery animate

Connecting the SignalR client to various servers

"Step-by-step guide on using JavaScript to print a PDF file stored locally

Whenever I press a button, my card holder gradually slides downwards

Tips for continuously prompting the user until a valid answer is obtained, and how to repeat this process N times

My function won't get called when utilizing Angular

Here is a method to transform the JSON object into a string as demonstrated below: