Tone.js/test/helper/Dispose.ts

export function isDisposed(instance): void {
	for (const prop in instance) {
		if (instance.hasOwnProperty(prop)) {
			const member = instance[prop];
			if (typeof member !== "function" &&
				typeof member !== "string" &&
				typeof member !== "number" &&
				typeof member !== "boolean" &&
				typeof member !== "undefined" &&
				prop !== "preset" &&
				!(member instanceof AudioContext)) {
				if (member !== null) {
					throw Error("property was not completely disposed: " + prop);
				}
			}
		}
	}
}