deepMerge.js

deepMerge.js

function deepMerge(a, b, path = []) {
	if (typeof a != 'object') return b;

	for (var key in b) {
		if (b[key] === undefined) {
			delete a[key];
			continue;
		}

		if (
			key in a &&
			key in b &&
			typeof a[key] != typeof b[key] &&
			a[key] !== null &&
			b[key] !== null
		) {
			throw new Error(
				'Incompatible types: ' +
					path.concat([key]).join('.') +
					' expected ' +
					typeof a[key] +
					' got ' +
					typeof b[key]
			);
		}

		Object.assign(a, {
			[key]: deepMerge(
				key in a ? a[key] : b[key],
				b[key],
				path.concat([key])
			),
		});
	}

	return a;
}

module.exports = deepMerge;