[JavaScript] 반복문

반복문

if

     //조건문
     //if, if~else, if~else if~else
     //switch~case
     //삼항 연산자
     var age = prompt('나이 입력')//값 입력
     age = parseInt(age)//정수로변환

     if(age>=20){//만약 age가 20이상이면
      alert("성인")
     }

if else

     //if~else if~else
     //점수 여러구간 체크~
     var score = prompt("점수입력")
     score = parseInt(score)

     if(score===100){
        document.write("A+","<br>")
     }else if(100>score && score>=90){//100>score>=90-X
      document.write("A","<br>")
     }else if(90>score && score>=80){
      document.write("B","<br>")
     }else if(80>score && score>=70){
      document.write("C","<br>")
     }else if(70>score && score>=60){
      document.write("D","<br>")
     }else{
      document.write("F","<br>")
     }

switch case

     //switch~case
     var num = prompt('숫자입력')
     num = parseInt(num)

     switch(num){
        case 1:
          document.write("One","<br>")
          break;
        case 2:
          document.write("Two","<br>")
          break;
        default://else
          document.write("I don't know","<br>")
          break;
     }

//---------------------------------------------------

      var alphabet=prompt('문자 입력')

      switch(alphabet){
        case 'a':
        case 'A':
          document.write("Apple","<br>")
          break;
        case 'b':
        case 'B':
          document.write("Banana","<br>")
          break;
      }

while

     // while, do~while, for
     // while : ~하는동안
     // 반복문의 3요소 : 초기식,조건식,증감식
     var i=1;//초기식
     var dan=7;
     while(i<=9){//조건식
        document.write(dan+"x"+i+"="+(dan*i),"<br>");
        i++;//증가식
     }

//---------------------------------------------------

     var i=1;//초기식
     var dan=7;
     while(i<=9){//조건식
        document.write(dan+"x"+i+"="+(dan*i),"<br>");
        i++;//증가식
     }

while 중첩

      var dan=2;

      while(dan<=9){
        var i=1
        while(i<=9){
          document.write(dan+"x"+i+"="+(dan*i),"<br>");
          i++;
        } 
        document.write("<br>");
        dan++
      }

do ~ while

      var i=4;
      do{
        document.write(i,"<br>");
        i++;
      }while(i<=3);

for

      var dan=7;
      for(var i=1; i<=9; i++){
        //document.write(dan+"x"+i+"="+(dan*i),"<br>");
        document.write(`${dan}x${i}=${dan*i}`,"<br>");
        //template string - ES6
        // ` - 백틱 (backtick), 역따옴표, 억양, 억양악센트 
        // '' ""
      }