What is the process of determining if two tuples are equal in Typescript?

Question

What is the process of determining if two tuples are equal in Typescript?

When comparing two tuples with equal values, it may be surprising to find that the result is false. Here's an example:

➜  algo-ts git:(master) ✗ ts-node
> const expected: [number, number] = [4, 4];
undefined
> const actual: [number, number] = [4, 4];
undefined
> actual == expected
false
> actual === expected
false

How should one properly compare tuples in a way that works regardless of their types?

typescript tuples

Answer 1

Answer №1

The reason for this is that you are comparing references of your tuples rather than checking the equality of each value.

If your tuples only consist of primitive data types, you can use a function like the following:

equals(expected:[number,number],actual:[number,number]): boolean{
    return expected[0] === actual[0] && expected[1] === actual[1];
}

However, if you want to compare tuples containing objects, you would need to create a custom equals function for those objects as well.

The implementation of an equals method varies depending on the specific type, so there is no universal solution for object equality.

Answer 2

The reason for this is that you are comparing references of your tuples rather than checking the equality of each value.

If your tuples only consist of primitive data types, you can use a function like the following:

equals(expected:[number,number],actual:[number,number]): boolean{
    return expected[0] === actual[0] && expected[1] === actual[1];
}

However, if you want to compare tuples containing objects, you would need to create a custom equals function for those objects as well.

The implementation of an equals method varies depending on the specific type, so there is no universal solution for object equality.

Answer 3

Answer №2

Array length comparison
Checking values without considering types using double equals

const arrA = [4, 4];
const arrB = [4, 4];

function compareArrays(arrA, arrB) {
  if (arrA.length != arrB.length) {
    return false; 
  }
  let areEqual = arrA.every((valueA, indexA) => valueA == arrB[indexA]);
  return areEqual;
}

console.log(compareArrays(arrA, arrB))

However, the arrays could contain object values, so a function is needed to check equality for both primitive and object types.

For better solutions, refer to reliable sources like lodash. https://github.com/lodash/lodash/blob/master/.internal/equalArrays.js

Additional information.

import { compareArrays } from './compareArrays';

describe('compareArrays', () => {
  test('number tuples', () => {
    const arrA: [number, number] = [4, 4];
    const arrB: [number, number] = [4, 4];
    expect(compareArrays(arrA, arrB)).toBe(true);
  });

  test('primitive tuples without objects', () => {
    const arrA: [boolean, number] = [false, 4];
    const arrB: [boolean, number] = [true, 4];
    expect(compareArrays(arrA, arrB)).toBe(false);
  });

  test('primitive tuples without objects', () => {
    const arrA: [string, number] = ['almel', 4];
    const arrB: [string, number] = ['shun', 4];
    expect(compareArrays(arrA, arrB)).toBe(false);
  });

  test('primitive tuples without objects', () => {
    const arrA: [string, number] = ['almel', 1];
    const arrB: [string, boolean] = ['almel', true];
    expect(compareArrays(arrA, arrB)).toBe(true); // because of double equals, number and boolean are considered equal
  });


  test('Double equals', () => {
    const arrA: [number, number] = [4, 4];
    const arrB: [number, number] = [4, 4];
     expect(arrA == arrB).toBe(false);
  });
});

I conducted tests using ts-jest, and all tests passed successfully. In the world of JavaScript, there are no tuple types; what we have are arrays.

Answer 4

Array length comparison
Checking values without considering types using double equals

const arrA = [4, 4];
const arrB = [4, 4];

function compareArrays(arrA, arrB) {
  if (arrA.length != arrB.length) {
    return false; 
  }
  let areEqual = arrA.every((valueA, indexA) => valueA == arrB[indexA]);
  return areEqual;
}

console.log(compareArrays(arrA, arrB))

However, the arrays could contain object values, so a function is needed to check equality for both primitive and object types.

For better solutions, refer to reliable sources like lodash. https://github.com/lodash/lodash/blob/master/.internal/equalArrays.js

Additional information.

import { compareArrays } from './compareArrays';

describe('compareArrays', () => {
  test('number tuples', () => {
    const arrA: [number, number] = [4, 4];
    const arrB: [number, number] = [4, 4];
    expect(compareArrays(arrA, arrB)).toBe(true);
  });

  test('primitive tuples without objects', () => {
    const arrA: [boolean, number] = [false, 4];
    const arrB: [boolean, number] = [true, 4];
    expect(compareArrays(arrA, arrB)).toBe(false);
  });

  test('primitive tuples without objects', () => {
    const arrA: [string, number] = ['almel', 4];
    const arrB: [string, number] = ['shun', 4];
    expect(compareArrays(arrA, arrB)).toBe(false);
  });

  test('primitive tuples without objects', () => {
    const arrA: [string, number] = ['almel', 1];
    const arrB: [string, boolean] = ['almel', true];
    expect(compareArrays(arrA, arrB)).toBe(true); // because of double equals, number and boolean are considered equal
  });


  test('Double equals', () => {
    const arrA: [number, number] = [4, 4];
    const arrB: [number, number] = [4, 4];
     expect(arrA == arrB).toBe(false);
  });
});

I conducted tests using ts-jest, and all tests passed successfully. In the world of JavaScript, there are no tuple types; what we have are arrays.

Answer 5

Answer №3

Once TypeScript code is transpiled into JavaScript, tuples are essentially treated as arrays in the resulting code. This raises the question of how to effectively compare two arrays for equality while taking order into consideration.

If you trust your TypeScript typings, you can adopt an approach similar to the one illustrated below which doesn't bother with checking array lengths and opts for a simple shallow comparison using ===.

const tuplesEqual = <T, U>(x: [T, U], y: [T, U]) => x.every((xVal, i) => xVal === y[i]);

This method is suitable for comparing two-tuples specifically, but extending it to support tuples of any length poses more of a challenge (although not necessarily impossible given the flexibility provided by TypeScript generics).

Answer 6

Once TypeScript code is transpiled into JavaScript, tuples are essentially treated as arrays in the resulting code. This raises the question of how to effectively compare two arrays for equality while taking order into consideration.

If you trust your TypeScript typings, you can adopt an approach similar to the one illustrated below which doesn't bother with checking array lengths and opts for a simple shallow comparison using ===.

const tuplesEqual = <T, U>(x: [T, U], y: [T, U]) => x.every((xVal, i) => xVal === y[i]);

This method is suitable for comparing two-tuples specifically, but extending it to support tuples of any length poses more of a challenge (although not necessarily impossible given the flexibility provided by TypeScript generics).

Answer 7

Answer №4

A straightforward method involves converting the tuples into strings and then comparing them.

One advantage of this method is that the string representations can be used in hashed collections such as Map<> and Set<>

For instance:

let tuple1 : [number, string] = [1,"example"];
let tuple2 : [number, string] = [1,"example"];

if (tuple1.toString() == tuple2.toString())
    console.log("tuple1 and tuple2 are identical");


let mySet = new Set<string>();

mySet.add([1,2].toString());

if (mySet.has([1,2].toString()))
    console.log("mySet includes the tuple [1,2]");

Answer 8

A straightforward method involves converting the tuples into strings and then comparing them.

One advantage of this method is that the string representations can be used in hashed collections such as Map<> and Set<>

For instance:

let tuple1 : [number, string] = [1,"example"];
let tuple2 : [number, string] = [1,"example"];

if (tuple1.toString() == tuple2.toString())
    console.log("tuple1 and tuple2 are identical");


let mySet = new Set<string>();

mySet.add([1,2].toString());

if (mySet.has([1,2].toString()))
    console.log("mySet includes the tuple [1,2]");

What is the process of determining if two tuples are equal in Typescript?

Answer №1

Answer №2

Answer №3

Answer №4

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