kvp-data-formats.md

name	Change Data Formats using Key-Value Pair
SPDX-FileCopyrightText	Copyright (c) 2026 Moddable Tech, Inc.
updated	2026-08-04

To override the default data type of buffer, specify the type in the format property to open().

Supported types are "buffer", "int8", "uint8", "int16", "uint16", "int32", "uint32", "int64", "uint64", and "string".

const settings = device.keyValue.open({
	path: "settings",
	format: "string"
});

settings.write("hello", "world");
trace(`${settings.read("hello")}\n`);

settings.write("json", JSON.stringify({ hello: "world" }));
trace(`${settings.read("json")}\n`);
let json = JSON.parse(settings.read("json"));

settings.close();

---

To change the data type of values after opening the domain, set the format property.

When reading a value, the format must match the format used when the value was written. There is no automatic type conversion.

const settings = device.keyValue.open({
	path: "settings"
});

settings.format = "string";
settings.write("hello", "world");
settings.format = "buffer";
settings.write("byte", Uint8Array.of(1));
settings.format = "uint32";
settings.write("32 bits", 0xffff_ffff);

settings.format = "string";
trace(`${settings.read("hello")}\n`);
settings.format = "buffer";
trace(`${new Uint8Array(settings.read("byte")).toHex()}\n`);
settings.format = "uint32";
trace(`${settings.read("32 bits")}\n`);

settings.close();