What is the best way to store a set of tuples in a collection so that each tuple is distinct and

Question

What is the best way to store a set of tuples in a collection so that each tuple is distinct and

I am working with TypeScript and aiming to create a collection of unique objects, each with distinct properties. The combinations of these properties within the collection must be one-of-a-kind.

For example, the following combinations would be considered valid:

[
    [ 1, 2 ],
    [ 2, 1 ],
]

However, attempting to add a duplicate combination such as [ 1, 2 ] would result in a "key already exists" error.

It's worth noting that my query assumes the presence of 3 keys representing the "composite key," but I am open to more flexible solutions if they exist.

In an attempt to address this challenge, I developed my own JavaScript-based "map-like" structure as a demonstration:

class MyCollection {
  constructor() {
    this.items = [];
  }

  add(firstTupleItem, secondTupleItem, thirdTupleItem) {
    if (this.has(firstTupleItem, secondTupleItem, thirdTupleItem)) {
      console.log(`ERR: Combination of [${firstTupleItem}, ${secondTupleItem}, ${thirdTupleItem}] already exists!`);

      return;
    }

    console.log(`Added combination of [${firstTupleItem}, ${secondTupleItem}, ${thirdTupleItem}]`);

    this.items.push([firstTupleItem, secondTupleItem, thirdTupleItem]);
  }

  has(firstTupleItem, secondTupleItem, thirdTupleItem) {
    return this.items.some(item =>
      item[0] === firstTupleItem &&
      item[1] === secondTupleItem &&
      item[2] === thirdTupleItem);
  }
}

const myCollection = new MyCollection();

/* passes as expected */

myCollection.add(1, 2, 3);
myCollection.add(2, 1, 3);
myCollection.add(3, 1, 2);
myCollection.add(1, 3, 2);

/* fails as expected */

myCollection.add(1, 2, 3);

console.log(myCollection.items);

While using a map could potentially offer improved efficiency, there may be concerns regarding the utilization of the value side. As an alternative concept, consider the following:

class MyCustomMap extends Map<[number, number, number], [number, number, number]> {
    addItem(item: [number, number, number]) {
        super.set(item, item);
    }
}

Is it necessary for me to create such a collection structure from scratch, or are there alternative, more efficient solutions available? (particularly within the context of TypeScript)

javascript typescript

Answer 1

Answer №1

Looking for a way to store unique values in JavaScript? Consider using a Set. This data structure ensures that each value is unique within the collection. However, it's important to note that the default equality check used by Set might not always meet your requirements. It follows the "same-value zero" equality rule, which behaves differently for objects like arrays compared to primitives like strings and numbers.

const a = [1, 2];
const b = [1, 2];
console.log(a === b); // false

const c = a;
console.log(a === c); // true

To customize the equality check for objects, you'll need to implement your own function. One approach is to convert objects to a primitive key using a method like JSON.stringify(). This ensures that two arrays are considered equal if their contents match.

Here's an example of how you can create a custom collection called MyCollection:

class MyCollection {
    private items: Map<string, Props> = new Map();
    add(...props: Props) {
        this.items.set(propsToKey(props), props);
        return this;
    }
    // Additional methods for managing the collection...
}

By implementing your custom equality function and using it in a Set or Map, you can ensure that values are uniquely stored based on your defined criteria.

Try out the code in the TypeScript playground.

Answer 2

Looking for a way to store unique values in JavaScript? Consider using a Set. This data structure ensures that each value is unique within the collection. However, it's important to note that the default equality check used by Set might not always meet your requirements. It follows the "same-value zero" equality rule, which behaves differently for objects like arrays compared to primitives like strings and numbers.

const a = [1, 2];
const b = [1, 2];
console.log(a === b); // false

const c = a;
console.log(a === c); // true

To customize the equality check for objects, you'll need to implement your own function. One approach is to convert objects to a primitive key using a method like JSON.stringify(). This ensures that two arrays are considered equal if their contents match.

Here's an example of how you can create a custom collection called MyCollection:

class MyCollection {
    private items: Map<string, Props> = new Map();
    add(...props: Props) {
        this.items.set(propsToKey(props), props);
        return this;
    }
    // Additional methods for managing the collection...
}

By implementing your custom equality function and using it in a Set or Map, you can ensure that values are uniquely stored based on your defined criteria.

Try out the code in the TypeScript playground.

What is the best way to store a set of tuples in a collection so that each tuple is distinct and

Answer №1

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