let text = "Please locate where 'locate' occurs!";
let index = text.indexOf("locate");
let lindex = text.lastIndexOf("locate");
let jindex = text.lastIndexOf("John"); // -1 if not found

console.log("index: " + index + " lindex: " + lindex + " jindex: " + jindex);

const letters = new Set(["a","b","c"]);
console.log(
  " letters = " + letters+
  "\n letters.size = " + letters.size+
  "\n letters.has('a') = " + letters.has("a")+
  "\n letters.add('d') = " + letters.add("d")+'        letters='+letters.values()+
  "\n letters.delete('a') = " + letters.delete("a")+ '       letters='+letters+
  "\n letters.clear() = " + letters.clear() + '       letters='+letters
)

const fruits = new Map([
  ["apples", 500],
  ["bananas", 300],
  ["oranges", 200]
]);

console.log(
  " fruits = " + fruits+
  "\n fruits.size = " + fruits.size+
  "\n fruits.get('apples') = " + fruits.get('apples')+
  "\n fruits.get('Apples') = " + fruits.get('Apples') +
  "\n fruits.has('apples') = " + fruits.has('apples')+
  // "\n fruits.set('grapes', 100) = " + fruits.set('grapes', 100)+ '       fruits='+JSON.stringify(Array.from(fruits.entries()))
  "\n fruits.set('grapes', 100) = " + fruits.set('grapes', 100)+ '       fruits='+[...fruits]+
  "\n fruits.delete('apples') = " + fruits.delete('apples')+ '       fruits='+[...fruits]+
  "\n fruits.clear() = " + fruits.clear() + '       fruits='+[...fruits]
)