redux-persist TypeScript migrations example

migrations.ts

interface RootStateV0 {
	a: {
		b: number;
	};
	d: {
		e: number;
	};
}

interface RootStateV1 {
	a: {
		b: number;
		c: string;
	};
	d: {
		e: string;
	};
}

interface RootStateV2 {
	a: {
		c: string;
	};
	d: {
		e: string;
	};
	f: string;
}

const migrations = {
	1: (state: RootStateV0): RootStateV1 => ({
		...state,
		a: {
			...state.a,
			c: 'default', // add string field
		},
		d: {
			e: `${state.d.e}`, // convert number field to string field
		},
	}),
	2: (state: RootStateV1): RootStateV2 => {
		const { b, ...aWithoutB } = state.a;
		return {
			...state,
			a: aWithoutB, // remove number field
			f: 'default', // add string field,
		};
	},
};