SearchAndReplace.js

// Perform a search and replace on the sentence using the arguments provided and return the new sentence.

// First argument is the sentence to perform the search and replace on.

// Second argument is the word that you will be replacing (before).

// Third argument is what you will be replacing the second argument with (after).

// Note: Preserve the case of the first character in the original word when you are replacing it. 
// For example if you mean to replace the word Book with the word dog, it should be replaced as Dog

function myReplace(str, before, after) {
    
    let index = str.indexOf(before);

    if (str[index] === str[index].toUpperCase()) {
        
      after = after.charAt(0).toUpperCase() + after.slice(1);
    } else {

      after = after.charAt(0).toLowerCase() + after.slice(1);
    }

    str = str.replace(before, after);
  
    return str;
  }
  
  // test here
  myReplace("A quick brown fox jumped over the lazy dog", "jumped", "leaped");