자바스크립트 : 배열 객체

01. 배열 속성 : length : 배열 길이 구하기 : 반환(숫자)
02. 배열 메서드 : join() : 배열 요소 문자열을 결합 : 반환(문자열) ★★★
03. 배열 메서드 : push() : 배열 마지막 요소에 추가 : 반환(숫자) ★★
03. 배열 메서드 : pop() : 배열 마지막 요소를 삭제 : 반환(삭제된 요소)
04. 배열 메서드 : unshift() : 배열 처음 요소에 추가 : 반환(숫자)
04. 배열 메서드 : shift() : 배열 처음 요소 삭제 : 반환(삭제된 요소)
05. 배열 메서드 : reverse() : 배열 요소의 순서를 반대로 정렬 : 반환(배열)
05. 배열 메서드 : sort() : 배열 요소를 정렬할 때 : 반환(배열)
06. 배열 메서드 : concat() : 배열 요소를 결합할 때 : 반환(배열)
07. 배열 메서드 : reduce() : 배열 요소를 하나로 정리 : 반환(결과값)
07. 배열 메서드 : reduceRight() : 배열 요소를 하나로 오른쪽부터 정리 : 반환(결과값)
08. 배열 메서드 : slice() : 배열 요소를 다른 요소로 변경 : 반환(배열) : ★★
09. 배열 메서드 : splice() : 배열 요소를 다른 요소로 변경 : 반환(배열) : ★★
10. 배열 메서드 : indexOf() : 배열 요소를 검색할 때 : 반환(숫자)
10. 배열 메서드 : lastIndexOf() : 배열 요소를 끝에서 검색할 때 : 반환(숫자)
10. 배열 메서드 : includes() : 배열 요소를 검색할 때 : 반환(불린)
11. 배열 메서드 : find() : 배열 요소를 검색할 때 : 반환(요소)
11. 배열 메서드 : findIndex() : 배열 요소를 검색할 때 : 반환(숫자)
12. 배열 메서드 : filter() : 조건에 만족하는 배열 요소를 검색할 때 : 반환(숫자)
13. 배열 메서드 : map() : 배열 요소를 추출하여 새로운 배열로 만듦 : 반환(숫자)
14. 배열 메서드 : Array.from() : 문자열을 배열로 변환 : 반환(결과값)

01. 배열 속성 : length

배열의 길이를 구하기 위해 사용하는 속성이다. 숫자로 반환한다.

번호	기본값	메서드	리턴값

// 1
const arrNum = [100, 200, 300, 400, 500];

document.querySelector(".sample01_N1").innerHTML = "1";
document.querySelector(".sample01_Q1").innerHTML = "[100, 200, 300, 400, 500]";
document.querySelector(".sample01_M1").innerHTML = "length";
document.querySelector(".sample01_P1").innerHTML = arrNum.length;

// 2
const arrTxt = ['a', 'b', 'c', 'd', 'f'];

document.querySelector(".sample01_N2").innerHTML = "2";
document.querySelector(".sample01_Q2").innerHTML = "['a', 'b', 'c', 'd', 'f']";
document.querySelector(".sample01_M2").innerHTML = "length";
document.querySelector(".sample01_P2").innerHTML = arrTxt.length;

// 3
const arr = [1, 2, ['a', 'b']];

document.querySelector(".sample01_N3").innerHTML = "3";
document.querySelector(".sample01_Q3").innerHTML = "[1, 2, ['a', 'b']]";
document.querySelector(".sample01_M3").innerHTML = "length";
document.querySelector(".sample01_P3").innerHTML = arr.length;

02. 배열 메서드 : join()

배열의 요소들을 연결하여 하나의 값으로 만든다. 문자열 값으로 반환한다.

번호	기본값	메서드	리턴값

const arrNum = [100, 200, 300, 400, 500];
// join 따옴표 안의 값을 출력될 데이터 사이사이에 넣음
const text1 = arrNum.join('');
const text2 = arrNum.join(' ');
const text3 = arrNum.join('★');
const text4 = arrNum.join('-');     // 전화번호 표기 등에 쓰이기 적합

03. 배열 메서드 : push() / pop()

push() 메서드는 배열 마지막 요소에 추가하여 숫자를 반환하고, pop() 메서드는 배열 마지막 요소를 삭제한다.

번호	기본값	메서드	리턴값	결과값

{
    //1
    const arrNum = [100, 200, 300, 400, 500];
    const arrPush = arrNum.push(600);

    document.querySelector(".sample03_N1").innerHTML = "1";
    document.querySelector(".sample03_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample03_M1").innerHTML = "push(600)"; //배열 마지막 요소에 600 추가
    document.querySelector(".sample03_P1").innerHTML = arrPush;     //6
    document.querySelector(".sample03_A1").innerHTML = arrNum;      //100,200,300,400,500,600

    //2
    const arrNum2 = [100, 200, 300, 400, 500];
    const arrPush2 = arrNum2.pop();

    document.querySelector(".sample03_N2").innerHTML = "2";
    document.querySelector(".sample03_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample03_M2").innerHTML = "pop()";      //배열 마지막 요소 500 삭제
    document.querySelector(".sample03_P2").innerHTML = arrPush2;     //500
    document.querySelector(".sample03_A2").innerHTML = arrNum2;      //100,200,300,400
}

04. 배열 메서드 : unshift() / shift()

unshift() 메서드는 배열 처음 요소에 추가하는 것이며, shift() 메서드는 배열 처음 요소에 삭제하는 것.

번호	기본값	메서드	리턴값	결과값

{
    const arrNum1 = [100, 200, 300, 400, 500];
    const arrNumUnshift = arrNum1.unshift(600);

    document.querySelector(".sample04_N1").innerHTML = "1";
    document.querySelector(".sample04_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample04_M1").innerHTML = "unshift()";
    document.querySelector(".sample04_P1").innerHTML = arrNumUnshift;
    document.querySelector(".sample04_A1").innerHTML = arrNum1;

    const arrNum2 = [100, 200, 300, 400, 500];
    const arrNumShift = arrNum2.shift();

    document.querySelector(".sample04_N2").innerHTML = "2";
    document.querySelector(".sample04_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample04_M2").innerHTML = "shift()";
    document.querySelector(".sample04_P2").innerHTML = arrNumShift;
    document.querySelector(".sample04_A2").innerHTML = arrNum2;
}

05. 배열 메서드 : reverse() / sort()

reverse() 메서드는 순서를 반대로 정렬하고, sort() 메서드는 배열 요소를 정렬한다.

번호	기본값	메서드	리턴값

{
    const arrNum1 = [100, 200, 300, 400, 500];
    const arrNumReverse = arrNum1.reverse();

    document.querySelector(".sample05_N1").innerHTML = "1";
    document.querySelector(".sample05_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample05_M1").innerHTML = "reverse()";
    document.querySelector(".sample05_P1").innerHTML = arrNumReverse;

    const arrNum2 = [100, 200, 300, 400, 500];
    const arrNumSort2 = arrNum2.sort();

    document.querySelector(".sample05_N2").innerHTML = "2";
    document.querySelector(".sample05_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample05_M2").innerHTML = "sort()";
    document.querySelector(".sample05_P2").innerHTML = arrNumSort2;

    const arrNum3 = [100, 300, 200, 400, 500];
    const arrNumSort3 = arrNum3.sort(function(a, b){return b - a});

    document.querySelector(".sample05_N3").innerHTML = "3";
    document.querySelector(".sample05_Q3").innerHTML = "[100, 300, 200, 400, 500]";
    document.querySelector(".sample05_M3").innerHTML = "sort(function(a, b){return b - a})";
    document.querySelector(".sample05_P3").innerHTML = arrNumSort3;

    const arrNum4 = [500, 400, 300, 200, 100];
    const arrNumSort4 = arrNum4.sort(function(a, b){return a - b});

    document.querySelector(".sample05_N4").innerHTML = "4";
    document.querySelector(".sample05_Q4").innerHTML = "[500, 400, 300, 200, 100]";
    document.querySelector(".sample05_M4").innerHTML = "sort(function(a, b){return a - b})";
    document.querySelector(".sample05_P4").innerHTML = arrNumSort4;

    const arrNum5 = ['c', 'b', 'e', 'w', 'h'];
    const arrNumSort5 = arrNum5.sort(function(a, b){ return a.localeCompare(b)});

    document.querySelector(".sample05_N5").innerHTML = "5";
    document.querySelector(".sample05_Q5").innerHTML = "['c', 'b', 'e', 'w', 'h']";
    document.querySelector(".sample05_M5").innerHTML = "a.localeCompare(b)";
    document.querySelector(".sample05_P5").innerHTML = arrNumSort5;

    const arrNum6 = ['c', 'b', 'e', 'w', 'h'];
    const arrNumSort6 = arrNum5.sort(function(a, b){ return b.localeCompare(a)});

    document.querySelector(".sample05_N6").innerHTML = "6";
    document.querySelector(".sample05_Q6").innerHTML = "['c', 'b', 'e', 'w', 'h']";
    document.querySelector(".sample05_M6").innerHTML = "b.localeCompare(a)";
    document.querySelector(".sample05_P6").innerHTML = arrNumSort6;
}

06. 배열 메서드 : concat() : 펼침연산자 : 배열 요소 결합

배열 두 개를 결합한다.

번호	기본값	메서드	리턴값

{
    const arrNum1 = [100, 200, 300];
    const arrNum2 = [400, 500, 600];
    const arrConcat = arrNum1.concat(arrNum2);

    document.querySelector(".sample06_N1").innerHTML = "1";
    document.querySelector(".sample06_Q1").innerHTML = "[100, 200, 300], [400, 500, 600]";
    document.querySelector(".sample06_M1").innerHTML = "arrNum1.concat(arrNum2)";
    document.querySelector(".sample06_P1").innerHTML = arrConcat;

    const arrSpered = [...arrNum1, ...arrNum2];

    document.querySelector(".sample06_N2").innerHTML = "2";
    document.querySelector(".sample06_Q2").innerHTML = "[100, 200, 300], [400, 500, 600]";
    document.querySelector(".sample06_M2").innerHTML = "[...arrNum1, ...arrNum2]";
    document.querySelector(".sample06_P2").innerHTML = arrSpered;
}

07. 배열 메서드 : reduce() / reduceRight()

배열 요소를 하나로 정리

번호	기본값	메서드	리턴값

{
    const arrNum1 = [100, 200, 300, 400, 500];
    const arrReduce1 = arrNum1.reduce(element => element);

    document.querySelector(".sample07_N1").innerHTML = "1";
    document.querySelector(".sample07_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample07_M1").innerHTML = "arrNum1.reduce(element => element)";
    document.querySelector(".sample07_P1").innerHTML = arrReduce1;

    const arrNum2 = [100, 200, 300, 400, 500];
    const arrReduce2 = arrNum2.reduce((p, c) => p + c);

    document.querySelector(".sample07_N2").innerHTML = "2";
    document.querySelector(".sample07_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample07_M2").innerHTML = "arrNum2.reduce((p, c) => p + c)";
    document.querySelector(".sample07_P2").innerHTML = arrReduce2;

    const arrNum3 = [100, 200, 300, 400, 500];
    let sum = 0;
    for(let i=0; i < arrNum3.length; i++) {
        sum += arrNum3[i];
    }

    document.querySelector(".sample07_N3").innerHTML = "3";
    document.querySelector(".sample07_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample07_M3").innerHTML = "for()";
    document.querySelector(".sample07_P3").innerHTML = sum;

    const arrNum4 = [[100, 200], [300, 400]];
    const arrReduce4 = arrNum4.reduce((p, c) => p.concat(c));

    document.querySelector(".sample07_N4").innerHTML = "4";
    document.querySelector(".sample07_Q4").innerHTML = "[[100, 200], [300, 400]]";
    document.querySelector(".sample07_M4").innerHTML = "arrNum4.reduce((p, c) => p.concat(c))";
    document.querySelector(".sample07_P4").innerHTML = arrReduce4;

    const arrNum5 = ["javascript", "react", "vue"];
    const arrReduce5 = arrNum5.reduceRight((p, c) => p+c);

    document.querySelector(".sample07_N5").innerHTML = "5";
    document.querySelector(".sample07_Q5").innerHTML = "['javascript', 'react', 'vue']";
    document.querySelector(".sample07_M5").innerHTML = "arrNum5.reduceRight((p, c) => p+c)";
    document.querySelector(".sample07_P5").innerHTML = arrReduce5;
}

08. 배열 메서드 : slice()

배열 요소를 하나로 정리

번호	기본값	메서드	리턴값

{
    const arrNum = [100, 200, 300, 400, 500];
    const result = arrNum.slice(2);

    document.querySelector(".sample08_N1").innerHTML = "1";
    document.querySelector(".sample08_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M1").innerHTML = "arrNum.slice(2)";
    document.querySelector(".sample08_P1").innerHTML = result;

    const result2 = arrNum.slice(2, 3);

    document.querySelector(".sample08_N2").innerHTML = "2";
    document.querySelector(".sample08_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M2").innerHTML = "arrNum.slice(2, 3)";
    document.querySelector(".sample08_P2").innerHTML = result2;

    const result3 = arrNum.slice(2, 4);

    document.querySelector(".sample08_N3").innerHTML = "3";
    document.querySelector(".sample08_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M3").innerHTML = "arrNum.slice(2, 4)";
    document.querySelector(".sample08_P3").innerHTML = result3;

    const result4 = arrNum.slice(2, 5);

    document.querySelector(".sample08_N4").innerHTML = "4";
    document.querySelector(".sample08_Q4").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M4").innerHTML = "arrNum.slice(2, 5)";
    document.querySelector(".sample08_P4").innerHTML = result4;

    const result5 = arrNum.slice(-2);

    document.querySelector(".sample08_N5").innerHTML = "5";
    document.querySelector(".sample08_Q5").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M5").innerHTML = "arrNum.slice(-2)";
    document.querySelector(".sample08_P5").innerHTML = result5;

    const result6 = arrNum.slice(-2, 5);

    document.querySelector(".sample08_N6").innerHTML = "6";
    document.querySelector(".sample08_Q6").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample08_M6").innerHTML = "arrNum.slice(-2, 5)";
    document.querySelector(".sample08_P6").innerHTML = result6;
}

09. 배열 메서드 : splice()

배열 요소를 다른 요소로 변경한다. slice()와는 달리 배열값도 바뀐다.

번호	기본값	메서드	리턴값	결과값

{
    const arrNum = [100, 200, 300, 400, 500];
    const result = arrNum.splice(2);
    
    document.querySelector(".sample09_N1").innerHTML = "1";
    document.querySelector(".sample09_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M1").innerHTML = "arrNum.splice(2)";
    document.querySelector(".sample09_P1").innerHTML = result;
    document.querySelector(".sample09_A1").innerHTML = arrNum;
    
    const arrNum2 = [100, 200, 300, 400, 500];
    const result2 = arrNum2.splice(2, 3);
    
    document.querySelector(".sample09_N2").innerHTML = "2";
    document.querySelector(".sample09_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M2").innerHTML = "arrNum.splice(2, 3)";
    document.querySelector(".sample09_P2").innerHTML = result2;
    document.querySelector(".sample09_A2").innerHTML = arrNum2;
    
    const arrNum3 = [100, 200, 300, 400, 500];
    const result3 = arrNum3.splice(2, 3, 'javascript');
    
    document.querySelector(".sample09_N3").innerHTML = "3";
    document.querySelector(".sample09_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M3").innerHTML = "arrNum.splice(2, 3, 'javascript')";
    document.querySelector(".sample09_P3").innerHTML = result3;
    document.querySelector(".sample09_A3").innerHTML = arrNum3;
    
    const arrNum4 = [100, 200, 300, 400, 500];
    const result4 = arrNum4.splice(1, 1, 'javascript');
    
    document.querySelector(".sample09_N4").innerHTML = "4";
    document.querySelector(".sample09_Q4").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M4").innerHTML = "arrNum.splice(1, 1, 'javascript')";
    document.querySelector(".sample09_P4").innerHTML = result4;
    document.querySelector(".sample09_A4").innerHTML = arrNum4;
    
    const arrNum5 = [100, 200, 300, 400, 500];
    const result5 = arrNum5.splice(1, 0, 'javascript');
    
    document.querySelector(".sample09_N5").innerHTML = "5";
    document.querySelector(".sample09_Q5").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M5").innerHTML = "arrNum.splice(1, 0, 'javascript')";
    document.querySelector(".sample09_P5").innerHTML = result5;
    document.querySelector(".sample09_A5").innerHTML = arrNum5;
    
    const arrNum6 = [100, 200, 300, 400, 500];
    const result6 = arrNum6.splice(0, 4, 'javascript');
    
    document.querySelector(".sample09_N6").innerHTML = "6";
    document.querySelector(".sample09_Q6").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample09_M6").innerHTML = "arrNum.splice(0, 4, 'javascript')";
    document.querySelector(".sample09_P6").innerHTML = result6;
    document.querySelector(".sample09_A6").innerHTML = arrNum6;
}

10. 배열 메서드 : indexOf() / lastIndexOf() / includes()

번호	기본값	메서드	리턴값

{
    const arrNum = [100, 200, 300, 400, 500];
    const arrIndex = arrNum.indexOf(200);

    document.querySelector(".sample10_N1").innerHTML = "1";
    document.querySelector(".sample10_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample10_M1").innerHTML = "arrNum.indexOf(200)";
    document.querySelector(".sample10_P1").innerHTML = arrIndex;

    const arrNum2 = [100, 200, 300, 400, 500];
    const arrIndex2 = arrNum2.indexOf(300);

    document.querySelector(".sample10_N2").innerHTML = "2";
    document.querySelector(".sample10_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample10_M2").innerHTML = "arrNum2.indexOf(300)";
    document.querySelector(".sample10_P2").innerHTML = arrIndex2;

    const arrNum3 = [100, 200, 300, 400, 500];
    const arrIndex3 = arrNum3.indexOf(600);

    document.querySelector(".sample10_N3").innerHTML = "3";
    document.querySelector(".sample10_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample10_M3").innerHTML = "arrNum3.indexOf(600)";
    document.querySelector(".sample10_P3").innerHTML = arrIndex3;

    const arrNum4 = [100, 200, 300, 400, 200];
    const arrIndex4 = arrNum4.lastIndexOf(200);

    document.querySelector(".sample10_N4").innerHTML = "4";
    document.querySelector(".sample10_Q4").innerHTML = "[100, 200, 300, 400, 200]";
    document.querySelector(".sample10_M4").innerHTML = "arrNum4.indexOf(600)";
    document.querySelector(".sample10_P4").innerHTML = arrIndex4;

    const arrNum5 = [100, 200, 300, 400, 200];
    const arrIndex5 = arrNum5.includes(200);

    document.querySelector(".sample10_N5").innerHTML = "5";
    document.querySelector(".sample10_Q5").innerHTML = "[100, 200, 300, 400, 200]";
    document.querySelector(".sample10_M5").innerHTML = "arrNum5.includes(200)";
    document.querySelector(".sample10_P5").innerHTML = arrIndex5;

    const arrNum6 = [100, 200, 300, 400, 200];
    const arrIndex6 = arrNum6.includes(600);

    document.querySelector(".sample10_N6").innerHTML = "6";
    document.querySelector(".sample10_Q6").innerHTML = "[100, 200, 300, 400, 200]";
    document.querySelector(".sample10_M6").innerHTML = "arrNum6.includes(600)";
    document.querySelector(".sample10_P6").innerHTML = arrIndex6;
}

11. 배열 메서드 : find() / findIndex()

번호	기본값	메서드	리턴값

{
    const arrNum = [100, 200, 300, 400, 500];

    // const result = arrNum.find(function(element) {
    //     return element === 300;
    // });
    // const result = arrNum.find((element) => {
    //     return element === 300;
    // });
    // const result = arrNum.find(element => {
    //     return element === 300;
    // });

    const result = arrNum.find(e => e === 300);

    document.querySelector(".sample11_N1").innerHTML = "1";
    document.querySelector(".sample11_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample11_M1").innerHTML = "arrNum.find(e => e === 300)";
    document.querySelector(".sample11_P1").innerHTML = result;

    const result2 = arrNum.find(e => e === 600);

    document.querySelector(".sample11_N2").innerHTML = "2";
    document.querySelector(".sample11_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample11_M2").innerHTML = "arrNum.find(e => e === 600)";
    document.querySelector(".sample11_P2").innerHTML = result2;

    const arrText = ['javascript', 'jquery', 'react'];
    const result3 = arrText.find(el => el === 'javascript');

    document.querySelector(".sample11_N3").innerHTML = "3";
    document.querySelector(".sample11_Q3").innerHTML = "['javascript', 'jquery', 'react']";
    document.querySelector(".sample11_M3").innerHTML = "arrText.find(el => el === 'javascript')";
    document.querySelector(".sample11_P3").innerHTML = result3;

    const result4 = arrText.findIndex(el => el === 'javascript');

    document.querySelector(".sample11_N4").innerHTML = "4";
    document.querySelector(".sample11_Q4").innerHTML = "['javascript', 'jquery', 'react']";
    document.querySelector(".sample11_M4").innerHTML = "arrText.findIndex(el => el === 'javascript')";
    document.querySelector(".sample11_P4").innerHTML = result4;

    const result5 = arrText.findIndex(el => el === 'html');

    document.querySelector(".sample11_N5").innerHTML = "5";
    document.querySelector(".sample11_Q5").innerHTML = "['javascript', 'jquery', 'react']";
    document.querySelector(".sample11_M5").innerHTML = "arrText.findIndex(el => el === 'html')";
    document.querySelector(".sample11_P5").innerHTML = result5;
}

12. 배열 메서드 : filter()

find() 메서드와 기능이 같지만 3번의 "el >= 300"처럼 더 활용성이 높다.

번호	기본값	메서드	리턴값

{
    const arrNum = [100, 200, 300, 400, 500];
    const result = arrNum.filter(el => el === 300);

    document.querySelector(".sample12_N1").innerHTML = "1";
    document.querySelector(".sample12_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample12_M1").innerHTML = "arrNum.filter(el => el === 300)";
    document.querySelector(".sample12_P1").innerHTML = result;

    const arrNum2 = [100, 200, 300, 400, 500];
    const result2 = arrNum2.filter(el => el === 600);

    document.querySelector(".sample12_N2").innerHTML = "2";
    document.querySelector(".sample12_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample12_M2").innerHTML = "arrNum2.filter(el => el === 600)";
    document.querySelector(".sample12_P2").innerHTML = result2;

    const arrNum3 = [100, 200, 300, 400, 500];
    const result3 = arrNum3.filter(el => el >= 300);

    document.querySelector(".sample12_N3").innerHTML = "3";
    document.querySelector(".sample12_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample12_M3").innerHTML = "arrNum3.filter(el => el >= 300)";
    document.querySelector(".sample12_P3").innerHTML = result3;
}

13. 배열 메서드 : map()

번호	기본값	메서드	리턴값

{
    const arrNum = [100, 200, 300, 400, 500];
    const result = arrNum.map(el => el);

    document.querySelector(".sample13_N1").innerHTML = "1";
    document.querySelector(".sample13_Q1").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample13_M1").innerHTML = "arrNum.map(el => el)";
    document.querySelector(".sample13_P1").innerHTML = result;

    const arrNum2 = [100, 200, 300, 400, 500];
    const result2 = arrNum2.map(el => el + "j");

    document.querySelector(".sample13_N2").innerHTML = "2";
    document.querySelector(".sample13_Q2").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample13_M2").innerHTML = "arrNum2.map(el => el + 'j')";
    document.querySelector(".sample13_P2").innerHTML = result2;

    const arrNum3 = [100, 200, 300, 400, 500];
    const result3 = arrNum3.map(el => el + 100);

    document.querySelector(".sample13_N3").innerHTML = "3";
    document.querySelector(".sample13_Q3").innerHTML = "[100, 200, 300, 400, 500]";
    document.querySelector(".sample13_M3").innerHTML = "arrNum3.map(el => el + 100)";
    document.querySelector(".sample13_P3").innerHTML = result3;

    // 가장 많이 쓰임
    const arrNum4 = [{a:100}, {a:200}, {a:300}];
    const result4 = arrNum4.map(el => el.a);

    document.querySelector(".sample13_N4").innerHTML = "4";
    document.querySelector(".sample13_Q4").innerHTML = "[{a:100}, {a:200}, {a:300}]";
    document.querySelector(".sample13_M4").innerHTML = "arrNum4.map(el => el.a)";
    document.querySelector(".sample13_P4").innerHTML = result4;
}

14. 배열 메서드 : Array.from()

번호	기본값	메서드	리턴값

{
    const text = "javascript";
    const result = Array.from(text);

    document.querySelector(".sample14_N1").innerHTML = "1";
    document.querySelector(".sample14_Q1").innerHTML = "'javascript'";
    document.querySelector(".sample14_M1").innerHTML = "Array.from(text)";
    document.querySelector(".sample14_P1").innerHTML = result;
    console.log(result);

    const text2 = "javascript";
    const result2 = Array.from(text2, el => el + "10");

    document.querySelector(".sample14_N2").innerHTML = "2";
    document.querySelector(".sample14_Q2").innerHTML = "'javascript'";
    document.querySelector(".sample14_M2").innerHTML = "Array.from(text2, el => el + '10')";
    document.querySelector(".sample14_P2").innerHTML = result2;
    console.log(result2);

    const text3 = "javascript";
    const result3 = [...text3].map(el => el);

    document.querySelector(".sample14_N3").innerHTML = "3";
    document.querySelector(".sample14_Q3").innerHTML = "'javascript'";
    document.querySelector(".sample14_M3").innerHTML = "[...text3].map(el => el)";
    document.querySelector(".sample14_P3").innerHTML = result3;
    console.log(result3);
}