SOURCE

 //1.while
 var i = 1; 
    var result = 0;
    while(i<=100){
        result=result+i;
        i++;
        }
        alert(result);

//2.do while
            var i = 0; 
            var result = 0;
            do{ i++;
                result=result+i;
            }while(i<100)
            alert(result);

//3.for
        var result = 0;
        for(var i = 1; i<=100 ; i++){
            result = result + i;
        }
        alert(result)