如何根据其值更改所需表单输入的CSS样式 [英] How to change the CSS style on required form inputs based on their values

问题描述

我想知道如何编写JavaScript来更改所需的表单元素的样式；并更改其中是否包含值.

I would like to know how to write the javascript to alter the style of form elements which are required; and change them if they have values in them.

我想要做的是在必填文本字段为空时在其周围有彩色边框，并在它们具有值时删除边框样式.

What I want to do is have a colored border around the required text fields when they are blank, and remove the border style when they have values.

我想做的是编写一个JavaScript函数来检查该值是否为空并设置适当的样式:

what I've thought of doing is to write a single javascript function which checks if the value is empty and set the appropriate style:

function requiredElement(id) {
  var Input = document.getElementById(id);
  if(Input.value==null) {
    Input.style.border = '2px solid #FF0000';
  }
}

但是我一直坚持的是，随着用户在这些必填字段中输入/删除字符，并为这些字段调用函数，更改样式.

But what I'm stuck with is changing the style as user enters/removes characters in these required fields, and calling the function for the fields.

我有一个简单的html表单，每个输入都有一个唯一的ID.

I have a simple html form, each input has a unique ID.

推荐答案

使用jQuery

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js" type="text/javascript"></script>

然后添加此代码:

$('.important').change(function() {
  if(($(this).val()) != '') $(this).css( 'border-width', '0' );
  else  $(this).css( 'border-width', '2' );
});

假设您在CSS中添加了边框

Assuming you added a border in the css

.important
{
    border-style:solid;
    border-width:2px;
    border-color:red;
}

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