JS determines whether the form input is null of sample code
- 2020-03-30 01:03:00
- OfStack
//Remove Spaces on both sides of the input string
function trim(s) {
var count = s.length;
var st = 0; // start
var end = count-1; // end
if (s == "") return s;
while (st < count) {
if (s.charAt(st) == " ")
st ++;
else
break;
}
while (end > st) {
if (s.charAt(end) == " ")
end --;
else
break;
}
return s.substring(st,end + 1);
}
Suppose the form looked like this:
<form action="testnew.html" name="form1">
username: <input type="text" name="name">
password: <input type="password" name="pwd"> <br>
<input type="submit" value=" submit " onclick="isEmpty()">
</form>
To determine whether the input is null, the function can be defined as follows:
function isEmpty(){
//Form1 is the name property & NBSP; in the form;
var _form = document.form1;
if(trim(_form.name.value)==""){
alert(" The username cannot be empty !");
return false;
}
if(trim(_form.pwd.value)==""){
alert(" The password cannot be empty !");
return false;
}
return true;
}