[Javascript][Lecture][드림코딩]자바스크립트 기초 강의(ES5+)(8/13)

8. 배열 제대로 알고 쓰자. 자바스크립트 배열 개념과 APIs 총정리 | 프론트엔드 개발자 입문편 (JavaScript ES6 )

"use strict";

// Array

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

// 2. Index position
const fruits = ["apple", "banana"];
console.log(fruits);
console.log(fruits.length);
console.log(fruits[0]);
console.log(fruits[1]);
console.log(fruits[2]);
console.log(fruits[fruits.length - 1]);
console.clear();
// 3. Looping over an array
// print all fruits
// a. for
for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

// b. for of
for (let fruit of fruits) {
  console.log(fruit);
}

// c. for each
// fruits.forEach(function (fruit, index) {
//   console.log(fruit, index);
// });

// fruits.forEach((fruit, index) => {
//   console.log(fruit, index);
// });

// fruits.forEach((fruit, index) => console.log(fruit, index));
fruits.forEach((fruit) => console.log(fruit));

// 4. Addtion, deletion, copy
// push: add an item to the end
fruits.push("strawberry", "peach");
console.log(fruits);

// pop: remove an item from the end
fruits.pop();
fruits.pop();
console.log(fruits);

// unshift: add an item to the beginning
fruits.unshift("strawberry", "peach");
console.log(fruits);

// shift: remove an item from the beginning
fruits.shift();
fruits.shift();
console.log(fruits);

// note!! shift, unshift are slower than pop, push: 나머지 전체가 움직여야 하기 때문에
// splice: remove an item by index position
fruits.push("strawberry", "peach", "lemon");
console.log(fruits);
fruits.splice(1, 1);
console.log(fruits);
fruits.splice(1, 1, "greenapple", "watermelon");
// fruits.splice(1, 0, "greenapple", "watermelon");
console.log(fruits);

// combine two arrays
const fruits2 = ["coconut", "durian"];
const newFruits = fruits.concat(fruits2);
console.log(newFruits);

// 5. Searching
// indexOf: find the index
console.clear();
console.log(fruits);
console.log(fruits.indexOf("apple"));
console.log(fruits.indexOf("lemon"));
console.log(fruits.indexOf("durian")); // 찾는 값이 없을 경우 -1을 출력

// includes
console.log(fruits.includes("durian"));
console.log(fruits.includes("peach"));

// lastIndexOf
console.clear();
fruits.push("apple");
console.log(fruits);
console.log(fruits.indexOf("apple")); // 첫번째 값의 index만 출력
console.log(fruits.lastIndexOf("apple")); // 마지막 값의 index만 출력