TIL 28. indexOf() - 요소 찾기

• indexOf() : 배열과 문자열에서 지정된 요소를 찾을 수 있는 '첫 번째 인덱스'를 반환하고
  존재하지 않으면 -1을 반환합니다.

배열

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];

console.log(beasts.indexOf('bison'));
// 1

// 2번 인덱스부터 찾기 시작
console.log(beasts.indexOf('bison', 2));
// 4

console.log(beasts.indexOf('giraffe'));
// -1

문자열

const paragraph = 'The quick brown fox jumps over the lazy dog. If the dog barked, was it really lazy?';

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

console.log(`The index of the first "${searchTerm}" from the beginning is ${indexOfFirst}`);
// The index of the first "dog" from the beginning is 40

console.log(`The index of the 2nd "${searchTerm}" is ${paragraph.indexOf(searchTerm, (indexOfFirst + 1))}`);
// The index of the 2nd "dog" is 52