String.prototype.indexOf()

const paragraph = "I think Ruth's dog is cuter than your dog!";

const searchTerm = "dog";
const indexOfFirst = paragraph.indexOf(searchTerm);

console.log(`The index of the first "${searchTerm}" is ${indexOfFirst}`);
// Expected output: "The index of the first "dog" is 15"

console.log(
  `The index of the second "${searchTerm}" is ${paragraph.indexOf(
    searchTerm,
    indexOfFirst + 1,
  )}`,
);
// Expected output: "The index of the second "dog" is 38"

str.indexOf(searchValue[, fromIndex])

"Blue Whale".indexOf("Blue"); // returns  0
"Blue Whale".indexOf("Blute"); // returns -1
"Blue Whale".indexOf("Whale", 0); // returns  5
"Blue Whale".indexOf("Whale", 5); // returns  5
"Blue Whale".indexOf("Whale", 7); // returns -1
"Blue Whale".indexOf(""); // returns  0
"Blue Whale".indexOf("", 9); // returns  9
"Blue Whale".indexOf("", 10); // returns 10
"Blue Whale".indexOf("", 11); // returns 10

"Blue Whale".indexOf("blue"); // returns -1

"Blue Whale".indexOf("Blue") !== -1; // true
"Blue Whale".indexOf("Bloe") !== -1; // false

var anyString = "Brave new world";

console.log(
  "The index of the first w from the beginning is " + anyString.indexOf("w"),
);
//  w   8
console.log(
  "The index of the first w from the end is " + anyString.lastIndexOf("w"),
);
//  w   10

console.log(
  'The index of "new" from the beginning is ' + anyString.indexOf("new"),
);
//  new   6
console.log(
  'The index of "new" from the end is ' + anyString.lastIndexOf("new"),
);
//  new   6

var myString = "brie, pepper jack, cheddar";
var myCapString = "Brie, Pepper Jack, Cheddar";

console.log('myString.indexOf("cheddar") is ' + myString.indexOf("cheddar"));
//  19 .
console.log(
  'myCapString.indexOf("cheddar") is ' + myCapString.indexOf("cheddar"),
);
//  -1 .

var str = "To be, or not to be, that is the question.";
var count = 0;
var pos = str.indexOf("e"); //pos 4  .

while (pos !== -1) {
  count++;
  pos = str.indexOf("e", pos + 1); //   e   e .
}

console.log(count); //  4 .