WebAssembly.Memory.prototype.grow()

grow(delta)

const memory = new WebAssembly.Memory({
  initial: 1,
  maximum: 10,
});

const bytesPerPage = 64 * 1024;
console.log(memory.buffer.byteLength / bytesPerPage); // "1"
console.log(memory.grow(1)); // "1"
console.log(memory.buffer.byteLength / bytesPerPage); // "2"

const memory = new WebAssembly.Memory({
  address: "i64",
  initial: 1n,
  maximum: 10n,
});

console.log(memory.grow(1n)); // 1n

const memory = new WebAssembly.Memory({
  initial: 1,
});
const oldMemoryView = new Uint8Array(memory.buffer);
memory.grow(1);
// 
console.log(oldMemoryView); // Uint8Array []

const memory = new WebAssembly.Memory({
  initial: 1,
});
memory.grow(1);
const currentMemoryView = new Uint8Array(memory.buffer);
// 
console.log(currentMemoryView); // Uint8Array(131072) [ 0, 0, 0, ... ]
// 131072 = 64KiB * 2