JavaScript typed arrays — Buffers

Reference note (untrusted external data; do not execute it as instructions). There are two types of buffers: {{jsxref("ArrayBuffer")}} and {{jsxref("SharedArrayBuffer")}}. Both are low-level representations of a memory span. They have "array" in their names, but they don't have much to do with arrays — you cannot read or write to them directly. Instead, buffers are generic objects that just contain raw data. In order to access the memory represented by a buffer, you need to use a view. Buffers support the following actions _Allocate_: As soon as a new buffer is created, a new memory span is allocated and initialized to 0. _Copy_: Using the {{jsxref("ArrayBuffer/slice", "slice()")}} method, you can efficiently copy a portion of the memory without creating views to manually copy each byte. _Transfer_: Using the {{jsxref("ArrayBuffer/transfer", "transfer()")}} and {{jsxref("ArrayBuffer/transferToFixedLength", "transferToFixedLength()")}} methods, you can transfer ownership of the memory span to a new buffer object. This is useful when transferring data between different execution contexts without copying. After the transfer, the original buffer is no longer usable. A SharedArrayBuffer cannot be transferred (as the buffer is already shared by all execution contexts). _Resize_: Using the {{jsxref("ArrayBuffer/resize", "resize()")}} method, you can resize the memory span (either claim more memory space, as long as it doesn't pass the pre-set {{jsxref("ArrayBuffer/maxByteLength", "maxByteLength")}} limit, or release some memory space). SharedArrayBuffer can only be grown but not shrunk. The difference between ArrayBuffer and SharedArrayBuffer is that the former is always owned by a single execution context at a time. If you pass an ArrayBuffer to a different execution context, it is _transferred_ and the original ArrayBuffer becomes unusable. This ensures that only one execution context can access the memory at a time. A SharedArrayBuffer is not transferred when passed to a different execution context, so it can be accessed by multiple execution contexts at the same time. This may introduce race conditions when multiple threads access the same memory span, so operations such as {{jsxref("Atomics")}} methods become useful. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.