Question

这是一个简单的javascript代码，用于显示错误消息，它现在可以正常工作如何向此代码添加一个语句，指出何时提交这些错误都不会显示成功消息。

JS

<script>
    $(document).ready(function() {
        $('#update').click(function() {
                var firstname = document.getElementById('fname').value;
                var lasttname = document.getElementById('lname').value;
                if (firstname.length < 2) {
                    $('#em').html('First name cannot be less than 2 characters');
                    return false;
                }
                if (lasttname.length < 2) {
                    $('#em').html('Last name cannot be less than 2 characters');
                    return false;
                }
                if (firstname.length > 15) {
                    $('#em').html('First name cannot be more than 15 characters');
                    return false;
                }
                if (lastname.length > 15) {
                    $('#em').html('Last name cannot be more than 15 characters');
                    return false;
                }
            }
        });
    });
</script>

Answer 1

只需添加一条语句，即可在所有success

的末尾显示if

$(document).ready(function() {
    $('#update').click(function() {
        var firstname = document.getElementById('fname').value;
        var lasttname = document.getElementById('lname').value;
        if (firstname.length < 2) {
            $('#em').html('First name cannot be less than 2 characters');
            return false;
        }
        if (lasttname.length < 2) {
            $('#em').html('Last name cannot be less than 2 characters');
            return false;
        }
        if (firstname.length > 15) {
            $('#em').html('First name cannot be more than 15 characters');
            return false;
        }
        if (lastname.length > 15) {
            $('#em').html('Last name cannot be more than 15 characters');
            return false;
        }
        $('#em').html('Everything looks fine'); //add a statement here
        return true; //return success
    });
});

提示：由于您已使用jquery，而不是使用document.getElementById用户jquery版本，如下所示：

var firstname = $('#fname').val();
var lasttname = $('#lname').val();

Answer 2

使用if-else子句而不是简单的if子句，并以显示成功消息的最后一个else子句结束：

<script>
$(document).ready(function() {
$('#update').click(function() {
var firstname=document.getElementById('fname').value;
var lasttname=document.getElementById('lname').value;
if(firstname.length<2)
{
$('#em').html('First name cannot be less than 2 characters');

} else if(lasttname.length<2)
{
$('#em').html('Last name cannot be less than 2 characters');

} else if(firstname.length > 15)
{
$('#em').html('First name cannot be more than 15 characters');

}else if(lastname.length > 15)
{
 $('#em').html('Last name cannot be more than 15 characters');

} else {
    $("#em").html("Congratulations!!!");
}
}
});
});
</script>

Answer 3

我可以在这里看到额外的结束}：

} //<------this
});
});

所以对于你的问题，你可以在底部添加：

var isvalid = firstname.length !== 0 && lastname.length !== 0;
if(isvalid){
   $('#em').html('SUCCESS!!');
}

Answer 4

你可以试试这个

<script>
$(document).ready(function() {
$('#update').click(function() {
var firstname=document.getElementById('fname').value;
var lasttname=document.getElementById('lname').value;
if(firstname.length<2)
{
$('#em').html('First name cannot be less than 2 characters');
return false;
}
else if(lasttname.length<2)
{
$('#em').html('Last name cannot be less than 2 characters');
return false;
}
else if(firstname.length > 15)
{
$('#em').html('First name cannot be more than 15 characters');
return false;
}
else if(lastname.length > 15)
{
 $('#em').html('Last name cannot be more than 15 characters');
 return false;
}
else{
$('#em').html('Success');
 return false;
}

});
});
</script>

使用javascript显示成功和错误消息

4 个答案: