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const 키워드로 만든 리액트 컴포넌트는 각 컴포넌트마다 독립적인 인스턴스가 생성되므로, 해당 컴포넌트의 내부에서 window 객체를 사용하더라도 전역 스코프의 window 객체와는 별개로 새로운 window 객체가 생성됩니다. 여기서 독립적인 인스턴스라는 것을 어떻게 아냐? 로 할당하면 새로운 인스턴스를 생성합니다. Object.is()를 통해서 a와 b의 인스턴스가 서로 다른 독립적인 인스턴스라는 것을 말해줍니다. import React from "react"; const Example1 = () => { var count = 0; function handleClick() { count++; console.log(`Count is now ${count}`); } return ( Count: {cou..

let과 const 키워드로 선언된 변수는 전역 객체의 프로퍼티로 등록되지 않습니다. 따라서, 이들 변수는 window 객체에서 찾을 수 없습니다. 예를 들어, 다음과 같이 let 키워드로 선언된 변수 myVariable을 사용할 때 window.myVariable을 출력해보면 undefined이 반환됩니다. let myVariable = 42; console.log(window.myVariable); // undefined 마찬가지로, const 키워드로 선언된 변수 myConstant를 사용할 때도 window.myConstant를 출력하면 undefined이 반환됩니다. const myConstant = "Hello, world!"; console.log(window.myConstant); // u..

interface에 정의된 name, age, address에 Object.keys한 느낌임 따라서 interface Person { name: string; age: number; } keyof Person // 'name' | 'age' interface Person { name: string; age: number; address: string; } type PersonKeys = keyof Person; function getProperty(obj: Person, key: keyof Person) { return obj[key]; } const person: Person = { name: 'John', age: 30, address: '123' } getProperty(person, 'name')..

문제 There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time. Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner. The tes..

문제 Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words. Note that the same word in the dictionary may be reused multiple times in the segmentation. Example 1: Input: s = "leetcode", wordDict = ["leet","code"] Output: true Explanation: Return true because "leetcode" can be segmented as "leet code"..

문제 You are given an array prices where prices[i] is the price of a given stock on the ith day. You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock. Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0. Example 1: Input: prices = [7,1,5,3,6,4] Output: 5 Expla..

문제 Given an integer numRows, return the first numRows of Pascal's triangle. In Pascal's triangle, each number is the sum of the two numbers directly above it as shown: Example 1: Input: numRows = 5 Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]] Example 2: Input: numRows = 1 Output: [[1]] Constraints: 1

문제 Given an m x n matrix board containing 'X' and 'O', capture all regions that are 4-directionally surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in that surrounded region. Example 1: Input: board = [["X","X","X","X"],["X","O","O","X"],["X","X","O","X"],["X","O","X","X"]] Output: [["X","X","X","X"],["X","X","X","X"],["X","X","X","X"],["X","O","X","X"]] Explanation: Notic..

문제 Given the root of a binary tree, return the inorder traversal of its nodes' values. Example 1: Input: root = [1,null,2,3] Output: [1,3,2] Example 2: Input: root = [] Output: [] Example 3: Input: root = [1] Output: [1] Constraints: The number of nodes in the tree is in the range [0, 100]. -100

문제 Given the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Example 1: Input: root = [3,9,20,null,null,15,7] Output: 3 Example 2: Input: root = [1,null,2] Output: 2 Constraints: The number of nodes in the tree is in the range [0, 104]. -100