SOURCE

 function getSum(){
            var sum = 0;
            for(var i = 1; i <= 100; i++) {
                sum += i;
            }
            console.log('1到100相加结果为：' + sum)


       
             var i = 0, sum = 0;
            while(i <= 99){
                 i ++;
             sum += i;
             }
             console.log('1到100相加结果为：' + sum)


             var i = 1, sum = 0;
             do{
                 sum += i
                 i++;
             }while(i<=100)
            console.log('1到100相加结果为：' + sum)
        }
        getSum()