Array

Declaration

//1.
const arr1 = new Array();
//2.
const arr2 = [1, 2];

index position

const fruits = ["사과", "바나나"];
console.log(fruits);
console.log(fruits.length);
console.log(fruits[0]); //첫 인덱스
console.log(fruits[1]);
console.log(fruits[2]);
console.log(fruits[fruits.length - 1]); //마지막 인덱스

Looping over an array

1) for

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

2) for..of

for (const fruitV of fruits) {
  console.log(fruitV);
}

3）forEach（コールバック関数）

fruits.forEach((value, index) => console.log(value, index));
console.log("---------------------------------");

fruits.forEach((value) => console.log(value));
console.log("===================================");

Add, Delete

push

fruits.push("딸기", "복숭아");
console.log(fruits);

pop

fruits.pop();
console.log(fruits);
fruits.pop();
console.log(fruits);

unshift

fruits.unshift("키위", "레몬");
console.log(fruits);

shift

fruits.shift();
console.log(fruits);
fruits.shift();
console.log(fruits);

splice

fruits.push("딸기", "복숭아", "레몬");
console.log(fruits);
fruits.splice(1, 1);
console.log(fruits);

fruits.splice(1, 1, "수박", "멜론");
console.log(fruits);

concat

const fruits2 = ["배", "구아바"];
const newFruits = fruits.concat(fruits2);
console.log(newFruits);

Searching

indexOf

console.log(fruits);
console.log(fruits.indexOf("사과"));
console.log(fruits.indexOf("수박"));
console.log(fruits.indexOf("구아바"));	//없으면 -1

includes

includes
console.log(fruits.includes("수박"));
console.log(fruits.includes("구아바"));

lastIndexOf

fruits.push("사과");
console.log(fruits);
console.log(fruits.indexOf("사과"));
console.log(fruits.lastIndexOf("사과"));