How can two arrays be effectively combined by their individual values?

Question

How can two arrays be effectively combined by their individual values?

Suppose I have an unspecified number of arrays all with the same length. My goal is to merge them into a single array.

When I say merge, I mean combining the values from each array into the output array.

Is there a function called merge(...arrays) that can achieve this?

Type Definition (potentially incorrect):

<T extends Array<U>, U>(...arr: T[]) => [...T][]

merge([A, B], [C, D]) → [[A, C], [B, D]]

Examples:

merge([1, 2, 3], [10, 20, 30]) → [[1, 10], [2, 20], [3, 30]]
merge([1, 2, 3]) → [[1], [2], [3]]

merge([1, "", {}], [17, { a: 1 }, "a"])

→

[[1, 17], ["", { a: 1 }], [{}, "a"]]

merge([]) → []

UPDATE: Additionally, please provide a TypeScript Type definition for the function.

javascript arrays typescript multidimensional-array

Answer 1

Answer №1

When working with TypeScript, it's not possible to directly determine the type of an element within an array. However, if you are dealing with arrays containing elements of a known type, you can utilize the type argument in your functions to assist in determining the type when returning results. Keep in mind that TypeScript cannot automatically infer whether an element within an array is an object with specific properties.

An excellent suggestion by @iota is to use Array.map() for this purpose. To enhance this approach, I've included a conditional check to throw an error if the arrays being compared do not have the same length.


function merge<U>(...arrs: Array<Array<U>>): U[][] {
    const { length: firstLength } = arrs[0];
    if (!arrs.every((arr) => arr.length == firstLength)) {
        throw new Error('Arrays are not the same size.');
    }
    return arrs[0].map((_, i)=>arrs.map(x => x[i]));
}
// Example usage: Arrays can be of any type
const a = merge<any>([1, "", {}], [17, { a: 1 }, "a"]);
// Output: a is any[][]

// Example usage: Arrays are comprised of numbers
const b = merge<number>([1, 2, 3], [10, 20, 30]);
// Output: b is number[][]

// Attempting to mix different types will result in a TypeScript error
const c = merge<number>([1, "", {}], [17, { a: 1 }, "a"]);
// Output: Type 'string' is not assignable to type 'number'.
//         Type '{}' is not assignable to type 'number'.

Answer 2

When working with TypeScript, it's not possible to directly determine the type of an element within an array. However, if you are dealing with arrays containing elements of a known type, you can utilize the type argument in your functions to assist in determining the type when returning results. Keep in mind that TypeScript cannot automatically infer whether an element within an array is an object with specific properties.

An excellent suggestion by @iota is to use Array.map() for this purpose. To enhance this approach, I've included a conditional check to throw an error if the arrays being compared do not have the same length.


function merge<U>(...arrs: Array<Array<U>>): U[][] {
    const { length: firstLength } = arrs[0];
    if (!arrs.every((arr) => arr.length == firstLength)) {
        throw new Error('Arrays are not the same size.');
    }
    return arrs[0].map((_, i)=>arrs.map(x => x[i]));
}
// Example usage: Arrays can be of any type
const a = merge<any>([1, "", {}], [17, { a: 1 }, "a"]);
// Output: a is any[][]

// Example usage: Arrays are comprised of numbers
const b = merge<number>([1, 2, 3], [10, 20, 30]);
// Output: b is number[][]

// Attempting to mix different types will result in a TypeScript error
const c = merge<number>([1, "", {}], [17, { a: 1 }, "a"]);
// Output: Type 'string' is not assignable to type 'number'.
//         Type '{}' is not assignable to type 'number'.

Answer 3

Answer №2

To achieve this, utilize the Array#map method.

function combineArrays(...arrays){
  return arrays[0].map((_, index)=>arrays.map(array => array[index]));
}
console.log(JSON.stringify(combineArrays([1, 2, 3], [10, 20, 30])));
console.log(JSON.stringify(combineArrays([1, 2, 3])));
console.log(JSON.stringify(combineArrays([1, "", {}], [17, { a: 1 }, "a"])));

Answer 4

To achieve this, utilize the Array#map method.

function combineArrays(...arrays){
  return arrays[0].map((_, index)=>arrays.map(array => array[index]));
}
console.log(JSON.stringify(combineArrays([1, 2, 3], [10, 20, 30])));
console.log(JSON.stringify(combineArrays([1, 2, 3])));
console.log(JSON.stringify(combineArrays([1, "", {}], [17, { a: 1 }, "a"])));

How can two arrays be effectively combined by their individual values?

Answer №1

Answer №2

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