문제 링크 : Existence of a Substring in a String and Its Reverse
/**
* @param {string} s
* @return {boolean}
*/
var isSubstringPresent = function(s) {
for(let i = 1; i < s.length; i++) {
let str = `${s[i]}${s[i-1]}`
if(s.includes(str)) return true;
}
return false;
};