Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

For example,
Given “egg”, “add”, return true.

Given “foo”, “bar”, return false.

Given “paper”, “title”, return true.

var isIsomorphic = function(s, t) {    var obj = {};    for(var i = 0; i < s.length; i++) {        var charS = s.charAt(i);        var charT = t.charAt(i);        if(obj[charS]){            if(obj[charS] != charT) {                return false            }        }else{            if(Object.values(obj).indexOf(charT) == -1){                obj[charS] = charT            }else{                return false            }        }    }    return true};