Javascript

 const str1 = "자바스크립트";
const str2 = "제이쿼리";
    
//document.write(str1 + str2);
//자바스크립트제이쿼리
document.querySelector(".sample01_N1").innerHTML = "1";
document.querySelector(".sample01_Q1").innerHTML = "자바스크립트, 제이쿼리";
document.querySelector(".sample01_M1").innerHTML = "문자열 결합";
document.querySelector(".sample01_P1").innerHTML = str1 + str2;

const num1 = 100;
const num2 = 200;

document.querySelector(".sample01_N2").innerHTML = "2";
document.querySelector(".sample01_Q2").innerHTML = "100, 200";
document.querySelector(".sample01_M2").innerHTML = "숫자(number) 결합";
document.querySelector(".sample01_P2").innerHTML = num1 + num2;

const text1 = "모던";
const text2 = "자바스크립트";
const text3 = "핵심";

//나는 모던(modern) 자바스크립트(javascript) 핵심을 배우고 싶다.
document.querySelector(".sample01_N3").innerHTML = "3";
document.querySelector(".sample01_Q3").innerHTML = "모던, 자바스크립트, 핵심";
document.querySelector(".sample01_M3").innerHTML = "문자열(string) 결합";
document.querySelector(".sample01_P3").innerHTML = "나는 "+ text1 + "(modern) " + text2 + "(javascript) " + text3 + "을 배우고 싶다.";

document.querySelector(".sample01_N3").innerHTML = "4";
document.querySelector(".sample01_Q3").innerHTML = "모던, 자바스크립트, 핵심";
document.querySelector(".sample01_M3").innerHTML = "템플릿 문자열";
document.querySelector(".sample01_P3").innerHTML = `나는 ${text1}(modern) ${text2}(javascript) ${text3}을배우고 싶다.`;

const str1 = "javascript";
const currestStr1 = str1.toUpperCase() 

document.querySelector(".sample02_N1").innerHTML = "1";
document.querySelector(".sample02_Q1").innerHTML = "javascript";
document.querySelector(".sample02_M1").innerHTML = "toUpperCase()";
document.querySelector(".sample02_P1").innerHTML =currestStr1;

const str2 = "JAVASCRIPT"
const currestStr2 = str2.toLowerCase() 

document.querySelector(".sample02_N2").innerHTML = "2";
document.querySelector(".sample02_Q2").innerHTML = "JAVASCRIPT";
document.querySelector(".sample02_M2").innerHTML = "toLowerCase()";
document.querySelector(".sample02_P2").innerHTML =currestStr2;

const str1 = "       javascript       ";
const currentStr1 = str1.trim();

document.querySelector(".sample03_N1").innerHTML = "1";
document.querySelector(".sample03_Q1").innerHTML = "str1";
document.querySelector(".sample03_M1").innerHTML = "trim()";
document.querySelector(".sample03_P1").innerHTML = currentStr1;

//console.log()공백확인 가능

const str2 = "       javascript       ";
const currentStr2 = str2.trimStart();

document.querySelector(".sample03_N2").innerHTML = "2";
document.querySelector(".sample03_Q2").innerHTML = "str2";
document.querySelector(".sample03_M2").innerHTML = "trimStart()";
document.querySelector(".sample03_P2").innerHTML = currentStr2;

const str3 = "       javascript       ";
const currentStr3 = str3.trimEnd();

document.querySelector(".sample03_N3").innerHTML = "3";
document.querySelector(".sample03_Q3").innerHTML = "str3";
document.querySelector(".sample03_M3").innerHTML = "trimEnd()";
document.querySelector(".sample03_P3").innerHTML = currentStr3;

const str1 = "javascript reference";
const currentStr1 = str1.slice(0);  //javascript reference
const currentStr2 = str1.slice(1); //avascript reference
const currentStr3 = str1.slice(2); //vascript reference
const currentStr4 = str1.slice(0, 1); //j
const currentStr5 = str1.slice(0, 2); //ja
const currentStr6 = str1.slice(0, 3); //jav
const currentStr7 = str1.slice(1, 2); //a
const currentStr8 = str1.slice(1, 3); //av
const currentStr9 = str1.slice(1, 4); //avs
const currentStr10 = str1.slice(-1); //e
const currentStr11 = str1.slice(-2); //ce
const currentStr12 = str1.slice(-3); //nce
const currentStr13 = str1.slice(-3, -1); //nc //-1 자리와 -3 자리르 바꾸면 더 큰 것이 앞으로 오기 때문에 값이 안 나옴!
const currentStr14 = str1.slice(-3, -2); //n
const currentStr15 = str1.slice(-3, -3); //

const currentStr16 = str1.slice(1, 4); //ava
const currentStr17 = str1.slice(4, 1); //'' 아무것도 안 나옴
const currentStr18 = str1.substring(1, 4); //ava
const currentStr19 = str1.substring(4, 1); //ava //substring은 slice와 다르게 자동으로 자리를 바꿔줘서 값이 다 나옴

const currentStr20 = str1.substr(0); //javascript reference
const currentStr21 = str1.substr(1); //avascript reference
const currentStr22 = str1.substr(2); //vascript reference
const currentStr23 = str1.substr(0, 1); //j
const currentStr24 = str1.substr(0, 2); //ja
const currentStr25 = str1.substr(0, 3); //jav
const currentStr26 = str1.substr(1, 2); //av
const currentStr27 = str1.substr(1, 3); //ava
const currentStr28 = str1.substr(1, 4); //avas
const currentStr29 = str1.substr(-1); //e
const currentStr30 = str1.substr(-2); //ce
const currentStr31 = str1.substr(-3); //nce
const currentStr32 = str1.substr(-1, 1); //e
const currentStr33 = str1.substr(-2, 2); //ce
const currentStr34 = str1.substr(-3, 3); //nce

//console.log(); -> 확인방법 

const str1 = "javascript reference";
const currentStr1 = str1.split(''); // ['j', 'a', 'v', 'a', 's', 'c', 'r', 'i', 'p', 't', ' ', 'r', 'e', 'f', 'e', 'r', 'e', 'n', 'c', 'e']
const currentStr2 = str1.split(' '); // ['javascript', 'reference']
const currentStr3 = str1.split('', 1); // ['j']
const currentStr4 = str1.split('', 2); // ['j', 'a']
const currentStr5 = str1.split(' ', 1); // ['javascript']
const currentStr6 = str1.split(' ', 2); // ['javascript', 'reference']
const currentStr7 = str1.split('j'); // ['', 'avascript reference']
const currentStr8 = str1.split('a'); // ['j', 'v', 'script reference']
const currentStr9 = str1.split('e'); // ['javascript r', 'f', 'r', 'nc', '']

const str2 = "java/script/refer/ence";
const currentStr10 = str2.split('/'); //['java', 'script', 'refer', 'ence']

const str3 = "java&script&refer!ence";
const currentStr11 = str3.split('!'); //['java&script&refer', 'ence']
const currentStr12 = str3.split('&'); //['java', 'script', 'refer!ence']
const currentStr13 = str3.split(/&|\!/); //정규식 표현 시작할때 : / 끝날때: / //['java', 'script', 'refer', 'ence']

const str4 = "javascript reference";
const currentStr14 = str4.split('').join(); //j,a,v,a,s,c,r,i,p,t, ,r,e,f,e,r,e,n,c,e join으로 배열 없어지고 문자열로 출력됨
const currentStr15 = str4.split('').join('*'); //j*a*v*a*s*c*r*i*p*t* *r*e*f*e*r*e*n*c*e
const currentStr16 = str4.split('').reverse().join(); //,c,n,e,r,e,f,e,r, ,t,p,i,r,c,s,a,v,a,j
const currentStr17 = str4.split('').reverse().join('/'); //e/c/n/e/r/e/f/e/r/ /t/p/i/r/c/s/a/v/a/j

//console.log(currentStr17); 

const str1 = "javascript reference";
const currentStr1 = str1.replace("javascript", "자바스크립트"); //자바스크립트 reference
const currentStr2 = str1.replace("j", "J"); //Javascript reference
const currentStr3 = str1.replace("e", "E"); //javascript rEference //제일 처음에 있는 e만 바뀜 //다 변경하고 싶을 때 replaceAll
const currentStr4 = str1.replaceAll("e", "E"); //javascript rEfErEncE
const currentStr5 = str1.replaceAll(/e/g, "E"); //javascript rEfErEncE //정규식 //g(global)는 모두 검색
const currentStr6 = str1.replaceAll(/e/gi, "E"); //javascript rEfErEncE //정규식 //i는 소문자 대문자 구별없이!

const str2 = "https://www.naver.com/img01.jpg";
const currentStr7 = str2.replace("img01.jpg", "img02.jpg"); //https://www.naver.com/img02.jpg

const str3 = "010-2000-1000";
const currentStr8 = str3.replace("-", ""); //0102000-1000
const currentStr9 = str3.replaceAll("-", ""); //01020001000 //All은 익스플로러 작동이 안됨
const currentStr10 = str3.replace(/-/g, ""); //01020001000 
const currentStr11 = str3.replace(/-/g, " "); //010 2000 1000
const currentStr12 = str3.replace(/-/g, "*"); //010*2000*1000
const currentStr13 = str3.replace(/[1-9]/g, "*"); //0*0-*000-*000

const str1 = "javascript";
const currentStr1 = str1.concat("reference") //javascriptreference
const currentStr2 = str1.concat(" ", "reference") //javascript reference
const currentStr3 = str1.concat(", ", "reference") //javascript, reference
const currentStr4 = str1.concat(", ", "reference", ", ", "book") //javascript, reference, book
const currentStr5 = str1.concat(", ", ["refer","book"]) //javascript, refer,book

const str1 = "javascript";
const currentStr1 = str1.repeat(0); //''
const currentStr2 = str1.repeat(1); //javascript
const currentStr3 = str1.repeat(2); //javascriptjavascript

const str1 = "456";
const currentStr1 = str1.padStart(1, "0"); //456
const currentStr2 = str1.padStart(2, "0"); //456
const currentStr3 = str1.padStart(3, "0"); //456
const currentStr4 = str1.padStart(4, "0"); //0456
const currentStr5 = str1.padStart(5, "0"); //00456
const currentStr6 = str1.padStart(6, "0"); //000456
const currentStr7 = str1.padStart(6, "1"); //111456
const currentStr8 = str1.padStart(6, "12"); //121456
const currentStr9 = str1.padStart(6, "123"); //123456
const currentStr10 = str1.padStart(6, "1234"); //123456
const currentStr11 = str1.padStart(6); //   456 //아무것도 안쓰면 남은 자릿수만큼 공백처리
    
const currentStr12 = str1.padEnd(1, "0"); //456
const currentStr13 = str1.padEnd(2, "0"); //456
const currentStr14 = str1.padEnd(3, "0"); //456
const currentStr15 = str1.padEnd(4, "0"); //4560
const currentStr16 = str1.padEnd(5, "0"); //45600
const currentStr17 = str1.padEnd(6, "0"); //456000
const currentStr18 = str1.padEnd(6, "1"); //456111
const currentStr19 = str1.padEnd(6, "12"); //456121
const currentStr20 = str1.padEnd(6, "123"); //456123
const currentStr21 = str1.padEnd(6, "1234"); //456123
const currentStr22 = str1.padEnd(6); //456___(공백)

const str1 = "javascript reference";
const currentStr1 = str1.indexOf("javascript");             //0
const currentStr2 = str1.indexOf("reference");              //11 ->위치값을 이야기함 시작이 11번째 부터
const currentStr3 = str1.indexOf("j");                      //0
const currentStr4 = str1.indexOf("a");                      //1
const currentStr5 = str1.indexOf("v");                      //2
const currentStr6 = str1.indexOf("jquery");                 //-1 ->데이터가 없을 때는 -1 출력
const currentStr7 = str1.indexOf("b");                      //-1 
const currentStr8 = str1.indexOf("javascript", 0);          //0
const currentStr9 = str1.indexOf("javascript", 1);          //-1 
const currentStr10 = str1.indexOf("reference", 0);          //11
const currentStr11 = str1.indexOf("reference", 1);          //11 
const currentStr12 = str1.indexOf("reference", 11);         //11 
const currentStr13 = str1.indexOf("reference", 12);         //-1 

const currentStr14 = str1.lastIndexOf("javascript");         //0 
const currentStr15 = str1.lastIndexOf("reference");         //11 
const currentStr16 = str1.lastIndexOf("j");                 //0 
const currentStr17 = str1.lastIndexOf("a");                 //3 
const currentStr18 = str1.lastIndexOf("v");                 //2 
const currentStr19 = str1.lastIndexOf("jquery");            //-1
const currentStr20 = str1.lastIndexOf("b");                 //-1 
const currentStr21 = str1.lastIndexOf("javascript", 0);     //0
const currentStr22 = str1.lastIndexOf("javascript", 1);     //0
const currentStr23 = str1.lastIndexOf("reference", 0);      //-1
const currentStr24 = str1.lastIndexOf("reference", 1);      //-1 
const currentStr25 = str1.lastIndexOf("reference", 11);     //11
const currentStr26 = str1.lastIndexOf("reference", 12);     //11

const str1 = "javascript reference";
const currentStr1 = str1.includes("javascript");             //true
const currentStr2 = str1.includes("j");                     //true
const currentStr3 = str1.includes("b");                     //false
const currentStr4 = str1.includes("reference");             //true
const currentStr5 = str1.includes("reference", 1);          //true
const currentStr6 = str1.includes("reference", 11);          //true
const currentStr7 = str1.includes("reference", 12);          //false

const str1 = "javascript reference";
const currentStr1 = str1.search("javascript");        //0
const currentStr2 = str1.search("reference");         //11 ->위치값을 이야기함 시작이 11번째 부터
const currentStr3 = str1.search("j");                 //0
const currentStr4 = str1.search("a");                 //1
const currentStr5 = str1.search("v");                 //2
const currentStr6 = str1.search("jquery");            //-1 ->데이터가 없을 때는 -1 출력
const currentStr7 = str1.search("b");                 //-1 
const currentStr8 = str1.search(/[a-z]/g);            //0 

const str1 = "javascript reference";
const currentStr1 = str1.match("javascript");       //javascript
const currentStr2 = str1.match("reference");       //reference
const currentStr3 = str1.match("r");               //r
const currentStr4 = str1.match(/reference/);       //reference
const currentStr5 = str1.match(/Reference/);       //null
const currentStr6 = str1.match(/Reference/i);      //reference
const currentStr7 = str1.match(/r/g);              //['r', 'r', 'r']
const currentStr8 = str1.match(/e/g);              //['e', 'e', 'e', 'e']

const str1 = "javascript reference";
const currentStr1 = str1.charAt();      //j
const currentStr2 = str1.charAt("0");   //j
const currentStr3 = str1.charAt("1");   //a
const currentStr4 = str1.charAt("2");   //v

//유니코드로 바꾸면
const currentStr5 = str1.charCodeAt();      //106 유니코드
const currentStr6 = str1.charCodeAt("0");   //106
const currentStr7 = str1.charCodeAt("1");   //97
const currentStr8 = str1.charCodeAt("2");   //118

 const str1 = "javascript reference"; 
const currentStr1 = str1.startWith('javascript');      //true
const currentStr2 = str1.startWith('j');               //true
const currentStr3 = str1.startWith('java');            //true
const currentStr4 = str1.startWith('reference');       //false
const currentStr5 = str1.startWith();                     //false
const currentStr6 = str1.startWith('');                   //true
const currentStr7 = str1.startWith('reference', 7);       //false
const currentStr8 = str1.startWith('reference',11);       //true

const currentStr9 = str1.endsWith('reference');      //true
const currentStr10 = str1.endsWith('e');               //true
const currentStr11 = str1.endsWith('refer');            //true
const currentStr12 = str1.endsWith('javascript');       //false
const currentStr13 = str1.endsWith();                     //false
const currentStr14 = str1.endsWith('');                   //true
const currentStr15 = str1.endsWith('reference', 7);       //false
const currentStr16 = str1.endsWith('reference',20);       //true