Unpack or unzip zip file contents using only web browser API's (no external dependencies)

unzip.js

/* Pass array buffer (probably read using readAsArrayBuffer() method) to unzip routine below, and it will return an array of object files containing their names and binary. */
/* Credits to cdauth post at https://stackoverflow.com/a/78762166/2100671 */
/* I also could not have made edits or understood this routine without a utility named zipdetails https://github.com/pmqs/zipdetails/tree/main */
const unzip = async function(zip_buffer) {
	const zip_array = new Uint8Array(zip_buffer);
	const data_view = new DataView(zip_buffer);
	const output = [];
	let index = 0;
	while(true) {
		const signature = data_view.getUint32(index, true);
		if(signature === 0x04034b50) { // local file info
			const file = {};
			const filename_length = data_view.getUint16(index + 26, true);
			const extra_length = data_view.getUint16(index + 28, true);
			const filename_bytes = new Uint8Array(zip_array.slice(index + 30, index + 30 + filename_length));
			file.filename = new TextDecoder('utf8').decode(filename_bytes);
			file.starts_at = index + 30 + filename_length + extra_length;
			file.compressed_size = data_view.getUint32(index + 18, true);
			file.compression_method = data_view.getUint16(index + 8, true);
			file.general_purpose_flag = data_view.getUint16(index + 6, true);
			file.stream_bit_is_set = (file.general_purpose_flag >> 3) & 0x1 === 1; // bit 3 has the "streamed" flag
			if(file.stream_bit_is_set) {
				let searching_for_stream_header = true;
				let search_index = file.starts_at;
				while(searching_for_stream_header) {
					const signature = data_view.getUint32(search_index, true);
					if(signature === 0x08074B50) { // streaming data info
						file.compressed_size = data_view.getUint32(search_index + 8, true);
						searching_for_stream_header = false;
					} else {
						search_index = search_index + 1;
					}
				}
			}
			const compressed_data_end = file.starts_at + file.compressed_size;
			const jump_to_index = file.stream_bit_is_set ? compressed_data_end + 16 : compressed_data_end;
			const raw_buffer = zip_array.slice(file.starts_at, compressed_data_end);
			if(file.compression_method === 0x00){ // "none", uncompressed/inflated
				file.buffer = raw_buffer;
			} else if (file.compression_method === 0x08) { // "DEFLATE", compressed/deflated
				file.buffer = await new Response(new Blob([raw_buffer]).stream().pipeThrough(new DecompressionStream('deflate-raw'))).arrayBuffer();
			} else {
				throw new Error(`Unsupported compression method 0x${file.compression_method.toString(16)}`);
			}
			index = jump_to_index;
			const is_directory = /\/$/.test(file.filename);
			if(!is_directory) {
				output.push(file);
			}
		} else if (signature === 0x02014b50) { // central directory info (this just gets jumped over)
			const filename_length = data_view.getUint16(index + 28, true);
			const extra_length = data_view.getUint16(index + 30, true);
			const comment_length = data_view.getUint16(index + 32, true);
			index = index + 46 + filename_length + extra_length + comment_length;
		} else if(signature === 0x06054b50) { // end of central directory
			break;
		} else {
			throw new Error(`Unsupported zip format signature 0x${signature.toString(16)}`);
		}
	}
	return output;
};