CODE EXAMPLE FOR JAVASCRIPT

Replace Char At Index Of String

function replaceAt(index, word, replacement)
{
let partOne =  word.substring(0, index) 

let partTwo =  word.substring(index,  word.length-1);
let answer = partOne + replacement + partTwo;
return answer;
}


var s = new String("AAAAA");
 

for(var i =0; i<s.length; i++)
{


    if(s[i]=="A")
    {
 
s= replaceAt(i, s, "@@@@");
  
    }
}
console.log(s);
/*console.log() @@@@@@@@@@@@@@@@@@@@*/