x++;和++x;的区别:
a. x++; 先使用,后进行加法运算;
b. ++x; 先进行加法运算,后使用;、
<script>
var n1=10;
var n2=20;
var n = n1++; //先把n1的值10赋值给n,此时n=10,后n1进行加法运算n1=11;
console.log(n); //10
console.log(n1); //11
n = ++n1 //先对n1进行加法运算,并把运算得到的值赋值给n,n=11+1;
console.log(n); //12
console.log(n1); //12
n = n2--;
console.log(n); //20
console.log(n2); //19
n = --n2;
console.log(n); //18
console.log(n2); //18
</script>