Tips for defining a distinct series of key-value pairs in typescript

Question

Tips for defining a distinct series of key-value pairs in typescript

Having experience with a different language where this was simple, I am finding it challenging to articulate a sequence of pairs:

Each pair is made up of two basic elements (such as strings or numbers)
Each element may appear multiple times within the list, but the combination must be unique:

a, k
a, m
b, m
b, n

The 2 key features I require are:

The ability to add a pair and ensure that if it already exists, it will not be duplicated (for example, attempting to add a, k to the current list would not result in a duplicate entry)
I should also be able to verify whether a specific pair exists in the list. For instance, checking for b, n should return true, while checking for b, p should return false.

What would be the most appropriate implementation in typescript?

Initially, my thought was to use Set<[string, string]>:

const a = new Set<[string, string]>();
a.add(['a', 'k']);
a.add(['a', 'm']);
a.add(['b', 'm']);
a.add(['b', 'n']);
...

However, the challenge arises when comparing objects, causing a.has(['a', 'b']) to return false. Are there any other alternatives worth considering?

javascript typescript

Answer 1

Answer №1

When using JS Set, element equality is checked using Object.is. This means that for arrays, the comparison is based on whether it is the same instance or the array itself.

To learn more about Set, visit MDN's page on Set

For information on equality comparisons and sameness in JavaScript, check out this link

If you're considering a different approach, you could create a class to store your arrays in stringified form:

class ArraySet<T extends any[]>  {
    values = new Set<string>();
    add: (arr: T) => this = (arr) => {
        this.values.add(JSON.stringify(arr));
        return this;
    }

    has: (arr: T) => boolean = (arr) => {
        return this.values.has(JSON.stringify(arr));
    }
}

const a = new ArraySet<[string, string]>();
a.add(['a', 'k']);
a.add(['a', 'm']);
a.add(['b', 'm']);
a.add(['b', 'n']);

console.log(a.has(['a', 'k']))

Further reading: Learn about storing arrays in ES6 Set and accessing them by value on Stack Overflow

Answer 2

When using JS Set, element equality is checked using Object.is. This means that for arrays, the comparison is based on whether it is the same instance or the array itself.

To learn more about Set, visit MDN's page on Set

For information on equality comparisons and sameness in JavaScript, check out this link

If you're considering a different approach, you could create a class to store your arrays in stringified form:

class ArraySet<T extends any[]>  {
    values = new Set<string>();
    add: (arr: T) => this = (arr) => {
        this.values.add(JSON.stringify(arr));
        return this;
    }

    has: (arr: T) => boolean = (arr) => {
        return this.values.has(JSON.stringify(arr));
    }
}

const a = new ArraySet<[string, string]>();
a.add(['a', 'k']);
a.add(['a', 'm']);
a.add(['b', 'm']);
a.add(['b', 'n']);

console.log(a.has(['a', 'k']))

Further reading: Learn about storing arrays in ES6 Set and accessing them by value on Stack Overflow

Answer 3

Answer №2

Have you considered developing your own custom solution for this task?

type Element = string | number
type ElementPair<T extends Element> = [T, T]

class ElementPairHolder<T extends Element> {
  private data: Map<Element, Set<Element>>;

  public constructor() {
    this.data = new Map();
  }

  public add(pair: ElementPair<T>): void {
    const [key, value] = pair;
    const set = this.data.get(key) ?? new Set();

    set.add(value);
    this.data.set(key, set);
  }

  public has(pair: ElementPair<T>): boolean {
    const [key, value] = pair;
    return this.data.get(key)?.has(value) ?? false;
  }
}

Here's an example of how you can use it:

const holder = new ElementPairHolder<string>();
holder.add(['a', 'k']);
holder.add(['a', 'm']);
holder.add(['b', 'm']);
holder.add(['b', 'n']);

console.log(holder.has(['b', 'n'])); // true
console.log(holder.has(['b', 'p'])); // false

Answer 4

Have you considered developing your own custom solution for this task?

type Element = string | number
type ElementPair<T extends Element> = [T, T]

class ElementPairHolder<T extends Element> {
  private data: Map<Element, Set<Element>>;

  public constructor() {
    this.data = new Map();
  }

  public add(pair: ElementPair<T>): void {
    const [key, value] = pair;
    const set = this.data.get(key) ?? new Set();

    set.add(value);
    this.data.set(key, set);
  }

  public has(pair: ElementPair<T>): boolean {
    const [key, value] = pair;
    return this.data.get(key)?.has(value) ?? false;
  }
}

Here's an example of how you can use it:

const holder = new ElementPairHolder<string>();
holder.add(['a', 'k']);
holder.add(['a', 'm']);
holder.add(['b', 'm']);
holder.add(['b', 'n']);

console.log(holder.has(['b', 'n'])); // true
console.log(holder.has(['b', 'p'])); // false

Tips for defining a distinct series of key-value pairs in typescript

Answer №1

Answer №2

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