includes

includes()

includes() 메서드는 문자열 포함 여부를 검색하여, 불린(true, false)을 반환합니다.
// "문자열, includes(검색값)"
// "문자열, includes(검색값, 시작값) "

const str1 = "javascript reference"
const currentStr1 = str1.includes("javascript");        //true  포함여부를 알려줌.
const currentStr2 = str1.includes("j");                 //true
const currentStr3 = str1.includes("b");                 //false
const currentStr4 = str1.includes("reference");         //true
const currentStr5 = str1.includes("reference", 1);      //true
const currentStr6 = str1.includes("reference", 11);     //true
const currentStr7 = str1.includes("reference", 12);     //false