使用JavaScript验证表单 [英] Validate a form using JavaScript

问题描述

  function validateForm（）{
 var x = document.forms [myForm] [fname] .value; 
 if（x == null || x ==）{
 alert（名字必须填写）; 
返回false; 
}} 
<！ -  html部分 - > 
< form name =myFormaction =demo_form.asponsubmit =return validateForm（）method =post> 
名字：< input type =textname =fname> 
< input type =submitvalue =提交> 
< / form>< br> 
  

这个代码的问题是按submit按钮触发 validateForm 函数。

解决方案

通过以下操作替换输入元素的代码：

 < input type =textonblur =return validateForm（）; NAME = FNAME > 
  

我猜这就是你要找的东西

I am a beginner and I have written a code for validating the form as:

function validateForm(){
var x=document.forms["myForm"]["fname"].value;
if (x==null || x==""){
alert("First name must be filled out");
return false;
  }}
  <!-- html part-->
<form name="myForm" action="demo_form.asp" onsubmit="return validateForm()" method="post">
First name: <input type="text" name="fname">
<input type="submit" value="Submit">
</form><br>

The problem with this code is pressing submit button triggers the validateForm function. How to call the function when the object losses focus?

解决方案

replace your input element's code by following

<input type="text" onblur="return validateForm();" name="fname">

i guess thats what you are looking for

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