SOURCE

document.write('<br/>-----------for循环----------<br/>');

var sum1 = 1;
var a = 1;
for (var i = 2; i <= 100; i++) {
    sum1 = sum1 + i;
    a = a + '+' + i;
    }
sum1 = sum1 + '=' + a;
document.write(sum1);

document.write('<br/>-----------while循环----------<br/>');

var i = 1;
var sum2 = 0;
while(i<=100){
    sum2 = sum2 + i;
    i++;
}
sum2 = sum2 + '=' + a;
document.write(sum2);

document.write('<br/>-----------do while循环----------<br/>');
var c = 1;
var sum3 = 0;
do{ 
    
    sum3 = sum3 + c;
    c++;   
}
while(c<=100){
    
    sum3 = sum3 + '=' + a;    
}
document.write(sum3);