search.js

function replace(str, before, after) {
var aslice = after.slice(1);
    if(before[0] === before[0].toUpperCase()){
      var caps = after.charAt(0).toUpperCase() + aslice;
      return str.replace(before, caps);
       }
    else if(after[0] === after[0].toUpperCase() && before[0] === before[0].toLowerCase()){
      var low = after.charAt(0).toLowerCase() + aslice;
      return str.replace(before, low);
    }
    else
      return str.replace(before,after);  
  }



replace("A quick brown fox jumped over the lazy dog", "jumped", "leaped");
replace("A quick brown fox jumped over the lazy dog", "jumped", "Leaped");