JavaScript文本框验证启用按钮

嘿，我有两个文本框和一个按钮。我只想在“playerName”文本框包含内容且“upperLimit”文本框包含大于0的整数时启用该按钮。 我希望该按钮开始禁用，然后随着用户在文本框中键入内容而动态更改，不断检查文本框中的内容，以查看是否应激活该按钮。以下是我尝试过的：

JavaScript:

var playerNameValid = false;
var upperLimitValid = false;


function validatePlayerName()
{
    if (document.getElementById("initialPlayerNameChoice").Value == "")
    {
        playerNameValid = false;
        document.getElementById("startGameButton").disabled = true;
    }
    else
    {
        playerNameValid = true;

        if (upperLimitValid == true)
        {
            document.getElementById("startGameButton").disabled = false;
        }
    }
}


function validateUpperLimit()
{
    if (isNaN(document.getElementById("initialUpperLimitChoice").valuetextContent))
    {
        upperLimitValid = false;
        document.getElementById("startGameButton").disabled = true;
    }
    else
    {
        upperLimitValid = true;

        if (playerNameValid == true)
        {
            document.getElementById("startGameButton").disabled = false;
        }
    }
}

标记：

<asp:Label ID="enterNameLabel" runat="server" Text="Enter your name: "></asp:Label>
<asp:TextBox ID="initialPlayerNameChoice" runat="server"></asp:TextBox>
<br /><br/>
<asp:Label ID="enterUpperLimitLabel" runat="server" Text="Enter upper limit: "></asp:Label>
<asp:TextBox ID="initialUpperLimitChoice" runat="server"></asp:TextBox>
<br /><br />
<asp:Button ID="startGameButton" enabled="false" runat="server" Text="Start Game" />

---

你几乎成功了。代码中只有几行需要修复：

if (document.getElementById("initialPlayerNameChoice").Value == "")
//In JavaScript there is no property called 'Value' -----^  use 'value' instead:
if (document.getElementById("initialPlayerNameChoice").value == "")


if (isNaN(document.getElementById("initialUpperLimitChoice").valuetextContent))
//Again, in JavaScript there is no property called 'valuetextContent' ---^
//Furthermore, 0 is a number, so if you kept this, the button would enable on 0
//You can use a regular expression to make sure it is a number > 0, and
//re-arranging your function eliminates re-checking of logic:
function validateUpperLimit()
{
  var num = document.getElementById("initialUpperLimitChoice").value.match(/^\d+$/);
  if(num && num[0] > 0)
  {
    upperLimitValid = true;

    if (playerNameValid == true)
    {
      document.getElementById("startGameButton").disabled = false;
    }
  }
  else
  {
    upperLimitValid = false;
    document.getElementById("startGameButton").disabled = true;
  }
}

您可以实现的另一个解决方案是只使用

validate（）

函数，并让两个字段都调用

onkeyup

。如果将验证函数更改为返回true或false，则可以消除全局变量的使用，并且逻辑更有意义

function validate(){
  if(validatePlayerName() && validateUpperLimit())
    document.getElementById('startGameButton').disabled = false;
  else
    document.getElementById('startGameButton').disabled = true;
}

function validatePlayerName(){
  if(document.getElementById('initialPlayerNameChoice').value != '')
    return true;
  else
    return false;
}

function validateUpperLimit(){
  var num = document.getElementById('initialUpperLimitChoice').value.match(/^\d+$/);
  if(num && num[0] > 0)
    return true;
  else
    return false;
}

然后是你的

onkeyup

代码（我认为你不需要

javascript:

部分，但我不完全确定，如果它对你咆哮，就把它扔回去）：

function validate(){
  if(validatePlayerName() && validateUpperLimit())
    document.getElementById('startGameButton').disabled = false;
  else
    document.getElementById('startGameButton').disabled = true;
}

function validatePlayerName(){
  if(document.getElementById('initialPlayerNameChoice').value != '')
    return true;
  else
    return false;
}

function validateUpperLimit(){
  var num = document.getElementById('initialUpperLimitChoice').value.match(/^\d+$/);
  if(num && num[0] > 0)
    return true;
  else
    return false;
}

initialPlayerNameChoice.Attributes.Add("onkeyup", "validate()");
initialUpperLimitChoice.Attributes.Add("onkeyup", "validate()");