Jsフロー制御文(二)循環文

主にfor、whileがあります.

  var age=prompt("       "); 
     if(age<18){
         alert("      "); //alert()        
     }else if(18>>>>>>>>>>
 var str="abc123";
    var num=parseInt(str)
    if (num==NaN){   //NaN          ，       
        alert(NaN);
    }else if(num==123){
        alert(123);
    }else if(typeof num=="number"){
        alert("num");
    }else{
        alert("str");
    }
    console.log(age);

while

"""
while(  ){
                    
        }
"""
        var i=1;
        while( i<=100){
            document.write(i+'
');
            i+=1;
        }

         #               
        #    do while
"""
        do{
                    
        }while(  )
"""
#  ：
        var j =1;
        do{
            if(j%2==0){
            console.log(j);
            }
            j++;
        }while(j<=10);
# >>>>
var sum=0;
        var n=1;
        while(n<=100){
            sum+=n;
            n++;
        }
        console.log(sum)

"""  for            ，while            """

break、徹底的に循環continueを退出します.今回の循環を終了し、次の循環を開始します.

var num=0;
        for(var i=1;i<10;i++){
            if(i%5==0){
                break;
            }
            console.log(i)
        }

        for(var i=0;i<=10;i++){
            if(i%5==0){
                continue;
            }
            console.log(i);
        }

多条件判定文法:new Date().getDay()機能:取得曜日戻り値:number(0-6)

var week = new Date().getDay();
        var weekstr = "";
        //        switch
        switch(week){
            case 0:
                // document.write("      ");//        
                weekstr = " ";
                break;
            case 1:
                // document.write("      ");//
                weekstr = " ";
                break;
            case 2:
                 weekstr = " ";
                // document.write("      ");
                break;
            case 3:
                 weekstr = " ";
                // document.write("      ");
                break;
            case 4:
                 weekstr = " ";
                // document.write("      ");
                break;
            case 5:
                 weekstr = " ";
                // document.write("      ");
                break;
            default:
                 weekstr = " ";
                // document.write("      ")
        }
        document.write("     " + weekstr)