Creating a string array within an array in TypeScript

Question

Creating a string array within an array in TypeScript

Struggling to return a type-safe Typescript v3.5 array without having to declare it within the method body? This array should consist of multiple string arrays.

Desiring something along the lines of:

 foo(): Array<Array<string>>:
    // perform some action

    return new Array<Array: string>>

Extra challenge: How can you return an array that contains arrays without explicitly declaring all those arrays in the code body?

LATEST UPDATE:

foo(): Array<Array<string>> {
    // determine 'someSize' and 'anotherSize'
    // initialize both arrays:
    let tempPartOfSpeechArr: string[] = new Array(someSize);
    let tempLinguisticUsageArr: string[] = new Array(anotherSize);

    let arrContainer = new Array(2);
    arrContainer[0] = tempPartOfSpeechArr;
    arrContainer[1] = tempLinguisticUsageArr;


    return arrContainer;

I just aim to return the arrContainer with both arrays inside. Trying to keep the code concise while maintaining readability.

typescript

Answer 1

Answer №1

If you want to quickly return an array literal, you can simply do so:

foo(): Array<Array<string>> {
    // Calculate 'someSize' and 'anotherSize'
    // Initialize both arrays:
    let tempPartOfSpeechArr: string[] = new Array(someSize);
    let tempLinguisticUsageArr: string[] = new Array(anotherSize);

    return [tempPartOfSpeechArr, tempLinguisticUsageArr]; // <===================
}

This method should be clear for those who are familiar with TypeScript. :-)

A quick note: Avoid using new Array or defining the length of your arrays unless necessary. You can simplify these lines:

let tempPartOfSpeechArr: string[] = new Array(someSize);
let tempLinguisticUsageArr: string[] = new Array(anotherSize);

by writing them like this:

let tempPartOfSpeechArr: string[] = [];
let tempLinguisticUsageArr: string[] = [];

The only difference is that creating sparse arrays in the original code (arrays with a defined length but no elements) can impact JavaScript engine optimizations.

Another note: It seems you're mixing two different styles of type declarations for arrays. While foo's return type is Array<Array<string>>, you declare arrays using string[]. You might consider using consistent array syntax by declaring foo as string[][]:

foo(): string[][] {
    // ....

For a complete example (check it out on the playground), here's a sample returning an array with unique non-digits and digits from a string:

function ex(str: string): string[][] {
    const a: string[] = [...new Set(str.replace(/\d/g, ""))];
    const b: string[] = [...new Set(str.replace(/\D/g, ""))];
    return [a, b];
}
console.log(ex("Testing 1 2 3 testing"));
// =>
// [
//   ["T", "e", "s", "t", "i", "n", "g"],
//   ["1", "2", "3"]
// ]

Answer 2

If you want to quickly return an array literal, you can simply do so:

foo(): Array<Array<string>> {
    // Calculate 'someSize' and 'anotherSize'
    // Initialize both arrays:
    let tempPartOfSpeechArr: string[] = new Array(someSize);
    let tempLinguisticUsageArr: string[] = new Array(anotherSize);

    return [tempPartOfSpeechArr, tempLinguisticUsageArr]; // <===================
}

This method should be clear for those who are familiar with TypeScript. :-)

A quick note: Avoid using new Array or defining the length of your arrays unless necessary. You can simplify these lines:

let tempPartOfSpeechArr: string[] = new Array(someSize);
let tempLinguisticUsageArr: string[] = new Array(anotherSize);

by writing them like this:

let tempPartOfSpeechArr: string[] = [];
let tempLinguisticUsageArr: string[] = [];

The only difference is that creating sparse arrays in the original code (arrays with a defined length but no elements) can impact JavaScript engine optimizations.

Another note: It seems you're mixing two different styles of type declarations for arrays. While foo's return type is Array<Array<string>>, you declare arrays using string[]. You might consider using consistent array syntax by declaring foo as string[][]:

foo(): string[][] {
    // ....

For a complete example (check it out on the playground), here's a sample returning an array with unique non-digits and digits from a string:

function ex(str: string): string[][] {
    const a: string[] = [...new Set(str.replace(/\d/g, ""))];
    const b: string[] = [...new Set(str.replace(/\D/g, ""))];
    return [a, b];
}
console.log(ex("Testing 1 2 3 testing"));
// =>
// [
//   ["T", "e", "s", "t", "i", "n", "g"],
//   ["1", "2", "3"]
// ]

Creating a string array within an array in TypeScript

Answer №1

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