index.js

'use strict';

module.exports = (string, separator) => {
	if (!(typeof string === 'string' && typeof separator === 'string')) {
		throw new TypeError('Expected the arguments to be of type `string`');
	}

	if (separator === '') {
		return [string];
	}

	const separatorIndex = string.indexOf(separator);

	if (separatorIndex === -1) {
		return [string];
	}

	return [
		string.slice(0, separatorIndex),
		string.slice(separatorIndex + separator.length)
	];
};