자바스크립트 : 배열 객체

01. 배열 속성 : legth : 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(결과값)
07. 배열 메서드 : reduce() : 배열 요소를 하나로 정리 : 반환(결과값)
07. 배열 메서드 : reduceRight() : 배열 요소를 하나로 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 요소 끝에서 검색할 때 : 반환(숫자)
10. 배열 메서드 : includes() : 배열 요소 검색할 때 : 반환(불린)
11. 배열 메서드 : find() : 배열 요소 검색할 때 : 반환(숫자) : ✨✨✨
11. 배열 메서드 : findIndex() : 배열 요소 검색할 때 : 반환(요소)
12. 배열 메서드 : filter() : 조건에 만족하는 배열 요소 검색할 때 : 반환(숫자) : ✨✨✨
13. 배열 메서드 : map() : 배열 요소를 추출하여 새로운 배열로 만듦 : 반환(배열)
14. 배열 메서드 : Array.from() : 문자열을 배열로 변환 : 반환(결과값)

01. 배열 속성 : legth : 배열 길이 구하기 : 반환(숫자)

length는 배열의 길이가 저장됩니다. 배열의 길이는 항상 배열의 마지막 요소의 값 보다 큰 값이 됩니다.

번호	기본값	메서드	리턴값

//01
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;
    
//02
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;
    
//03
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() : 배열 요소 문자열을 결합 : 반환(문자열)

번호	기본값	메서드	리턴값

//01
const arrNum = [100, 200, 300, 400, 500];
const text1 = arrNum.join('');
const text2 = arrNum.join(' ');
const text3 = arrNum.join('✨');
const text4 = arrNum.join('-');

03. 배열 메서드 : push() / pop()

push()메서드는 베열 마지막 요소에 추가 하고, pop()메서드는 배열 마지막 요소를 제거합니다.

번호	기본값	메서드	리턴값	결과값

//01
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)";
document.querySelector(".sample03_P1").innerHTML = arrPush;   //6
document.querySelector(".sample03_A1").innerHTML = arrNum;    //100,200,300,400,500,600
    
//02
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()";
document.querySelector(".sample03_P2").innerHTML = arrPush2;   //500
document.querySelector(".sample03_A2").innerHTML = arrNum2;    //100,200,300,400

04. unshift() / shift()

unshift() 메서드는 배열 처음 요소에 추가, shift() 메서드는 배열 처음 요소에 삭제

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(100);

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. reverse() / sort()

reverse() 메서드는 순서를 반대로 정렬, sort() 메서드는 배열 요소를 정렬

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

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

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

document.querySelector(".sample05_N4").innerHTML = "4";
document.querySelector(".sample05_Q4").innerHTML = "[300, 400, 500, 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 = "sort(function(a,b){ return a.localeCompare(b)})";
document.querySelector(".sample05_P5").innerHTML = arrNumSort5;

const arrNum6 = ['c', 'b', 'e', 'w', 'h'];
const arrNumSort6 = arrNum6.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 = "sort(function(a,b){ return b.localeCompare(a)})";
document.querySelector(".sample05_P6").innerHTML = arrNumSort6;

06. concat()

배열 요소를 결합할 때 사용, 결과값을 반환합니다.

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(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 = "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 = "reduceRight((p,c) => p + c)";
document.querySelector(".sample07_P5").innerHTML = arrReduce5;

08. slice()

배열 요소를 다른 요소로 변경 : 반환(배열) - 원래값에 영향을 미치지 않음

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. splice()

배열 요소를 다른 요소로 변경(원본값이 바뀜)

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 = "arrNum3.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 = "arrNum4.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 = "arrNum5.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 = "arrNum6.splice(0, 4, 'javascript')";
document.querySelector(".sample09_P6").innerHTML = result6;   
document.querySelector(".sample09_A6").innerHTML = arrNum6;

10. indexOf() / lastIndexOf() / includes()

indexOf() 메서드는 배열 요소를 검색할 때 사용,lastIndexOf() 메서드는 배열 요소 끝에서 검색할 때 사용, includes() 메서드는 배열 요소가 있는지 없는지 검색

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.lastIndexOf(200)";
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. find() / findIndex()

find() 메서드는 배열 요소 검색할 때 사용하며 반환은 숫자로 합니다 ,findIndex() 메서드는 배열 요소 검색할 때 사용하며 반환은 요소로 합니다.

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, 200]";
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, 200]";
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. filter()

조건을 걸 수 있음(find와 다른 점)

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. map()

map() 메서드는 배열 요소를 추출하여 새로운 배열로 만듭니다.

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; 

const arrNum4 = [{a:100}, {a:200}, {a:300}];        //객체로 감싸져 있어야만 사용가능
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. Array.from()

Array.from() 메서드는 문자열을 배열로 변환 시켜준다.

번호	기본값	메서드	리턴값

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

console.log(result);    //['j', 'a', 'v', 'a', 's', 'c', 'r', 'i', 'p', 't']

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; 

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; 

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;