Handling spread of a union of tuples in TypeScript

Handling spread of a union of tuples in TypeScript

If you have been working with TypeScript, you might have come across a situation where you need to handle the spread of a union of tuples. This can be a bit tricky, but fear not, we have some solutions for you.

Solution 1: Using a type guard

One way to handle the spread of a union of tuples is by using a type guard. This involves checking the type of the tuple and then using the spread operator accordingly. Here’s an example:

type Tuple = [string, number] | [boolean, string];

function handleSpread(tuple: Tuple) {
  if (Array.isArray(tuple)) {
    const [a, b] = tuple;
    // Do something with a and b
  } else {
    const [a, b, c] = tuple;
    // Do something with a, b, and c
  }
}

// Usage
handleSpread(["hello", 42]); // Tuple is [string, number]
handleSpread([true, "world", 42]); // Tuple is [boolean, string]

In this example, we have a type guard that checks if the tuple is an array. If it is, we destructure the array into variables a and b. If it’s not, we destructure it into variables a, b, and c. You can then perform the desired operations based on the number of elements in the tuple.

Solution 2: Using a discriminated union

Another solution is to use a discriminated union. This involves adding a discriminant property to each tuple in the union, which can be used to determine the type of the tuple. Here’s an example:

type Tuple = [string, number] | [boolean, string];

function handleSpread(tuple: Tuple) {
  if ("0" in tuple) {
    const [a, b] = tuple;
    // Do something with a and b
  } else {
    const [a, b, c] = tuple;
    // Do something with a, b, and c
  }
}

// Usage
handleSpread(["hello", 42]); // Tuple is [string, number]
handleSpread([true, "world", 42]); // Tuple is [boolean, string]

In this example, we check if the property “0” exists in the tuple. If it does, we destructure the tuple into variables a and b. If it doesn’t, we destructure it into variables a, b, and c. This way, we can determine the type of the tuple based on the presence of the discriminant property.

These are two solutions for handling the spread of a union of tuples in TypeScript. Choose the one that suits your needs and implement it in your code. Happy coding!

Final HTML:

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type Tuple = [string, number] | [boolean, string];

function handleSpread(tuple: Tuple) {
  if (Array.isArray(tuple)) {
    const [a, b] = tuple;
    // Do something with a and b
  } else {
    const [a, b, c] = tuple;
    // Do something with a, b, and c
  }
}

// Usage
handleSpread(["hello", 42]); // Tuple is [string, number]
handleSpread([true, "world", 42]); // Tuple is [boolean, string]

type Tuple = [string, number] | [boolean, string];

function handleSpread(tuple: Tuple) {
  if ("0" in tuple) {
    const [a, b] = tuple;
    // Do something with a and b
  } else {
    const [a, b, c] = tuple;
    // Do something with a, b, and c
  }
}

// Usage
handleSpread(["hello", 42]); // Tuple is [string, number]
handleSpread([true, "world", 42]); // Tuple is [boolean, string]