TypeScript Array.prototype.at() Method

The Array.prototype.at() method in TypeScript allows you to access elements in an array using both positive and negative indices. It returns the element stored at the specified index if the index is valid, otherwise it returns undefined.

Syntax:

array.at(index: number): T | undefined

Parameter:

• index: It takes the index of the element whose value it will return.

Return Value:

• Returns the element which is stored at the given index position. If the given index position is invalid then it will return undefined.

Examples of Array.prototype.at() Method

Example 1: Accessing Elements with Valid Indices

In this example, we will demonstrate how to access elements using both positive and negative indices.

Example 1: The below code will demonstrate that how to access elements by passing valid negative and positive both kinds of indices as parameters.

const arr: (number | string | boolean)[] = [1, 2, "TypeScript", false, true];

console.log(`Passed index is 1, will return 2nd element: ${arr.at(1)}`); 

console.log(`Passed index is -1, will return last value element: ${arr.at(-1)}`); 

console.log(`Passed index is 2, will return 3rd element: ${arr.at(2)}`); 

Output:

Passed index is 1, will return 2nd element: 2
Passed index is -1, will return last value element: true
Passed index is 2, will return 3rd element: TypeScript

Example 2: Handling Invalid Indices

In this example, we will show the behavior of the at() method when passing invalid index positions.

const arr: (number | string | boolean)[] = [1, 2, "TypeScript", false, true];

console.log(`Passed invalid index as -5: ${arr.at(-5)}`); 

console.log(`Passed invalid index as 6: ${arr.at(6)}`); 

console.log(`Passed invalid index as -7: ${arr.at(-7)}`);

Output:

Passed invalid index as -5: undefined
Passed invalid index as 6: undefined
Passed invalid index as -7: undefined

pankajbind

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Article Tags :

• JavaScript
• Web Technologies
• TypeScript