For example, rev(12345) will return 54321, and rev(123) will return 321. There is no limit to the number of integer digits.
function sum(a){
var s = 0;
while(a){// The first time 123 The second time 12 The third time 1 The fourth time 0 stops the loop
s=s*10 +a%10;// 3 30+2 320+1
a=parseInt(a/10);//12 1 0
}
return s;
}
console.log(sum(123));
The second method
function wei(a){
//用for
for (var i = 1; true; i ++) {
if(parseInt(a/Math.pow(10,i)) < 1){
return i;
}
}
//用while
// var i = 0;
// while(true){
// i++;
// if(a/Math.pow(10,i)<1){
// // console.log(i);
// return i;
// }
// }
}
function rev(b){
var n = wei(b);
var tol = 0;
for(var i=1;i<=n;i++){
tol +=parseInt(b/Math.pow(10,i-1))%10*(Math.pow(10,n-i));
}
alert(b+"'s inverse"+tol);
}
var c = parseInt(prompt());
rev(c);