JavaScript Typed Arrays — Interview Questions & Answers

Ques: What are Typed Arrays in JavaScript?

Ans: Typed Arrays are array-like objects that allow you to read and write raw binary data directly from memory buffers. They are not the same as normal arrays — they are used for high-performance numerical and binary operations.

Example:

const buffer = new ArrayBuffer(8);
const view = new Int32Array(buffer);
view[0] = 42;
console.log(view[0]); // 42

Ques: Why were Typed Arrays introduced in JavaScript?

Ans: Typed Arrays were introduced to:

Work with binary data directly.
Improve performance for numeric calculations.
Enable WebGL, WebAssembly, and streaming data.
Support low-level operations like image and audio processing.

Ques: What are the main components of Typed Arrays?

Ans: There are two main parts:

ArrayBuffer – a fixed-size memory area that stores raw bytes.
TypedArray View – a specific view to interpret those bytes (like Int8Array, Float32Array, etc.).

Example:

const buffer = new ArrayBuffer(16);
const int32 = new Int32Array(buffer);

Ques: What are some common Typed Array types?

Typed Array	Bytes per Element	Range
`Int8Array`	1	-128 to 127
`Uint8Array`	1	0 to 255
`Int16Array`	2	-32,768 to 32,767
`Uint16Array`	2	0 to 65,535
`Int32Array`	4	-2,147,483,648 to 2,147,483,647
`Uint32Array`	4	0 to 4,294,967,295
`Float32Array`	4	Decimal values
`Float64Array`	8	Higher precision decimals

Ques: What is the difference between Array and TypedArray?

Feature	Regular Array	Typed Array
Data Type	Any type (mixed)	Fixed numeric type
Size	Dynamic	Fixed
Performance	Slower	Faster (binary access)
Use Case	General JS data	Binary / numeric data
Memory	Not contiguous	Contiguous (better for performance)

Ques: How do you create a Typed Array in JavaScript?

Ans: There are multiple ways:

// Create with length
const arr1 = new Uint8Array(4);

// From an array
const arr2 = new Float32Array([1.5, 2.5, 3.5]);

// From an ArrayBuffer
const buffer = new ArrayBuffer(8);
const arr3 = new Int16Array(buffer);

Ques: What is an ArrayBuffer?

Ans: ArrayBuffer is a fixed-length block of memory used to store raw binary data.

It cannot be accessed directly — you must use a TypedArray view or DataView.

Example:

const buffer = new ArrayBuffer(16);
console.log(buffer.byteLength); // 16 bytes

Ques: What is a DataView in JavaScript?

Ans: DataView provides more control over reading/writing data with different types and byte orders (endianness).

const buffer = new ArrayBuffer(8);
const view = new DataView(buffer);
view.setInt8(0, 100);
console.log(view.getInt8(0)); // 100

Ques: What are some useful Typed Array properties?

Property	Description
`.buffer`	References the underlying ArrayBuffer
`.byteLength`	Number of bytes occupied
`.length`	Number of elements
`.BYTES_PER_ELEMENT`	Size per element in bytes

Example:

const arr = new Int16Array(4);
console.log(arr.BYTES_PER_ELEMENT); // 2

Ques: What are common Typed Array methods?

Method	Description
`.set()`	Copy array values into another TypedArray
`.subarray(start, end)`	Creates a new view of a part of the array
`.slice()`	Copies a section
`.map()`, `.forEach()`, `.filter()`	Work like Array methods
`.fill()`	Fills array with a static value
`.reverse()`, `.sort()`	Same as regular Array methods

Example:

const arr = new Uint8Array([10, 20, 30]);
arr.set([40, 50], 1);
console.log(arr); // [10, 40, 50]

Ques: How can you convert a Typed Array to a normal Array?

const typed = new Float32Array([1.1, 2.2, 3.3]);
const normal = Array.from(typed);
console.log(normal); // [1.1, 2.2, 3.3]

Ques: What are Typed Array use cases in real-world applications?

Handling binary file data (images, audio, PDFs)
WebGL and 3D rendering
Machine learning numeric calculations
Video and game development
Data compression/decompression

Ques: What is BYTES_PER_ELEMENT used for?

Ans: It tells how many bytes each element of the typed array uses.

console.log(Int32Array.BYTES_PER_ELEMENT); // 4

Ques: What is the role of byteOffset in Typed Arrays?

Ans: Specifies the starting point (in bytes) for the view inside the ArrayBuffer.

const buffer = new ArrayBuffer(8);
const view = new Int16Array(buffer, 2); // starts at byte 2

Ques: What is a WeakSet, and is it similar to Typed Arrays?

Ans: No, a WeakSet stores object references only and has no relation to Typed Arrays.

Typed Arrays work with binary numeric data, not objects.

Ques: How do you copy part of one Typed Array into another?

const a = new Uint8Array([1, 2, 3]);
const b = new Uint8Array(3);
b.set(a);
console.log(b); // [1, 2, 3]

Ques: Can you resize a Typed Array?

Ans: No, Typed Arrays have a fixed size.

If you need resizing — create a new Typed Array and copy values.

Ques: Are Typed Arrays iterable?

Ans: Yes, they can be looped using for...of.

const arr = new Int8Array([5, 10, 15]);
for (let value of arr) console.log(value);

Ques: How are Typed Arrays different from DataView?

Feature	TypedArray	DataView
Purpose	Simple, uniform view	Fine-grained control
Type	Fixed (like Int8Array)	Custom per operation
Use Case	Fast numeric data	Parsing mixed binary data

Ques: Can Typed Arrays handle floating-point numbers?

Ans: Yes, with Float32Array and Float64Array.

const floats = new Float32Array([1.5, 2.75, 3.9]);
console.log(floats[1]); // 2.75

Ques: What happens if you assign out-of-range values?

Ans: The values are clamped or wrapped according to type range.

const arr = new Int8Array(1);
arr[0] = 200; // wraps around
console.log(arr[0]); // -56