Question

我正在为我的javascript类做一个表单，而我却陷入了它的某个部分。我有一个单独的验证器javascript文件，并在html文件上调用该函数。如果未填写表单区域，则所有验证都有效。我想要做的是，如果字段留空，则验证将失败并将值插入该字段。下面是表单字段，html页面中的javascript函数和外部验证程序js文件的示例。

html head中的调用函数：

function formvalidation(thisform) {
with (thisform) {
if (textbox_validation(first_name,"Please enter your first name.")==false)
{first_name.blur(); return false;};
if (textbox_validation(business_name,"Please enter your business. Please enter N/A if 
you do not have one.")==false) { business_name.focus(); return false; 
business_name.value=="N/A";};

外部js验证器：

function textbox_validation(entered, alertbox) {
with (entered) {
if (value==null || value=="") {
  alert(alertbox);
  return false;
}
else {
  return true;
   }
  }
}

因此验证器工作并专注于空字段，但对于我的一些字段，我希望它们在验证失败或未填充int时用自己的特定值填充。 business_name代码行是我尝试使其工作的时候。非常感谢任何帮助！

Answer 1

使用DOM设置字段的占位符。像这样。

 var myInput = document.getElementById('input1');
 myInput.placeholder = 'This validation has failed.';

Answer 2

通常情况下，您不会使用提醒，而是将错误消息放在span或div附近input或form的顶部（或底部） {1}}。另外（如@Frits van Campen所述）， generally bad practice to use with 尝试这样的事情：

function textbox_validation(entered, errormsg) {
    var errbox = document.getElementById(entered.id + '-errors'); // just to prevent writing it twice
    // Note this requires the input to have an id, and the errer box's id to be the same with an '-errors' suffix.

    // Instead of using with, just acces properties normally
    if (!entered.value) { // The `!` "neggation" operater makes "falsy" values `true`
                      // "falsy" values include `false`, the empty string, `0`, `null`, `undefined`, `NaN` and a few others
        // Put the error message in the DOM instead of alerting it
        errbox.innerHTML = errormsg;
        return false;
    }
    else {
        // Wipe any previous error messages
        errbox.innerHTML = '';
        return true;
    }
}

对于表单验证器，再次;我们不要使用with。但是，当尝试将“N / A”分配给该值时，您使用了比较运算符而不是赋值运算符，并且您已经完成了<返回后坚强> ：

function formvalidation(thisform) {
    // just use the `!` "negation" operator
    if (!textbox_validation(thisform.first_name,
        "Please enter your first name."))
    {
        thisform.first_name.blur();
        return false;
    }
    if (!textbox_validation(business_name,
        "Please enter your business. Please enter N/A if you do not have one."))
    {
        thisform.business_name.focus();
        thisform.business_name.value = "N/A"; // for assignment, use `=`. `==` and `===` are used for comparison
        return false; // a return statement ends the function, make sure it's after anything you want to execute!
    }
}

验证后，Javascript填充表单

2 个答案: