const consistsRepeatedSubstring = (str) => `${str}${str}`.indexOf(str, 1) !== str.length;
const consistsRepeatedSubstring = (str: string): boolean => `${str}${str}`.indexOf(str, 1) !== str.length;
consistsRepeatedSubstring('aa'); // trueconsistsRepeatedSubstring('aaa'); // trueconsistsRepeatedSubstring('ababab'); // trueconsistsRepeatedSubstring('abc'); // false