Use a generator function to partition a blob and upload blocks sequentially to Azure Storage

blob-generator-function.ts

async function putBlocks(blob: Blob, url: string): Promise<string[]> {
	const blockIds: string[] = []

	let baseUrl = url + '&comp=block'

	for (let { block, blockId } of partitionBlob(blob, BLOCK_SIZE)) {
		blockIds.push(blockId)
		await fetch(`${baseUrl}&blockid=${blockId}`, {
			...DEFAULT_FETCH_SETTINGS,
			headers: {
				'x-ms-blob-type': 'BlockBlob'
			},
			body: block
		})
	}

	return blockIds
}

function* partitionBlob(blob: Blob, partitionSize: number): Generator<{ block: Blob, blockId: string }, void> {
	const totalBlocks = Math.ceil(blob.size / partitionSize)
	let blockPointer = 0

	for (let blockIndex = 0; blockIndex < totalBlocks; blockIndex++) {
		let nextBlockPointer = blockPointer + partitionSize
		yield {
			block: blob.slice(blockPointer, Math.min(nextBlockPointer, blob.size)),
			blockId: getBlockId(blockIndex)
		}
		blockPointer = nextBlockPointer
	}

	return
}