The growable 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 array is constructed. If a maxByteLength option was set in the constructor, growable will return true; if not, it will return false.

In this example, we create a 8-byte buffer that is growable to a max length of 16 bytes, then check its growable property, growing it if growable returns true:

const buffer = new SharedArrayBuffer(8, { maxByteLength: 16 });

if (buffer.growable) {
  console.log("SAB is growable!");
  buffer.grow(12);
}

• SharedArrayBuffer
• SharedArrayBuffer.prototype.grow()
• SharedArrayBuffer.prototype.maxByteLength