var a;
// var a=100;//第一行为100
function yubianyi(a){
document.write(a,'<br>');//underfine
a=100;
document.write(a,'<br>');//100
var a=10;
document.write(a,'<br>');//10
}
yubianyi(a);
var a;
// var a=100;//第一行为100
function yubianyi(a){
document.write(a,'<br>');//underfine
a=100;
document.write(a,'<br>');//100
var a=10;
document.write(a,'<br>');//10
}
yubianyi(a);