How to Declare the Return Type of a Generic Arrow Function to be an Array ?

In TypeScript, declaring the return type of a generic arrow function to be an array is generally essential when we want to ensure that the function always returns the array of a particular type. This is especially necessary for maintaining type safety and maintaining consistency in our code. Declaring the return type as an array, one can avoid unintentional errors and make code more easy to understand. There are several methods to declare the return type of a generic arrow function to be an array which are as follows:

Using generic type parameters

We can use a generic type parameter to specify the type of elements in the array. This method provides flexibility as it allows the function to return an array of any type.

Syntax:

The syntax for declaring the return type of a generic arrow function to be an array:

const function_name = (): Array<RetrunType> => {
  // Function Body
}

EXample: Creating an array of squared values from 1 to 25 using TypeScript arrow function with explicit return type.

Javascript

const myArr = (): Array<string> => {
  const arr = [];
  for (let i = 0; i < 5; i++) {
    arr.push(`${(i + 1) ** 2}`);
  }
  return arr;
};

const resultArr = myArr();
console.log(resultArr);

Output:

["1", "4", "9", "16", "25"] 

Without using generic type parameter

We can specify or declare the array type without using a generic type parameter. This method is convenient when we need to implement a particular type of the elements in the array.

Syntax:

The syntax for declaring the return type of a generic arrow function to be an array:

const function_name = (): returnType[] => {
  // Function Body
}

Example: Generating a string array with elements “Element 0” to “Element 4” using a concise TypeScript arrow function.

Javascript

const myStrArr = (): string[] => {
  const arr = [];
  for (let i = 0; i < 5; i++) {
    arr.push(`Element ${i}`);
  }
  return arr;
};

const resultStrArr = myStrArr();
console.log(resultStrArr);

Output:

["Element 0", "Element 1", "Element 2", "Element 3", "Element 4"]