The byteLength accessor property of SharedArrayBuffer instances returns the length (in bytes) of this SharedArrayBuffer.
The byteLength property is an accessor property whose set accessor function is undefined, meaning that you can only read this property. The value is established when the shared array is constructed and cannot be changed.
Note that these examples cannot be run directly from the console or an arbitrary web page, because SharedArrayBuffer is not defined unless its security requirements are met.
const sab = new SharedArrayBuffer(1024);
sab.byteLength; // 1024