var sentence = "Hello";
let word = sentence.split("");
let result = "";

for (let i = 0; i < word.length; i++) {
  let element = word[i];
  //console.log(element.charCodeAt());
  let temp = element.charCodeAt();

  if (temp >= 65 && temp <= 90) {
    let nouvelleIndex = Number(temp +32);
    let ter = String.fromCharCode(nouvelleIndex);
    result += ter;
    //console.log(ter);
    } else {
      result +=element;
    }
}
console.log(result);