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嘿，所以我有两个文本框和一个按钮。我只希望在“playerName”文本框包含某些内容并且“upperLimit”文本框包含整数 > 0 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，不断检查中的内容文本框来查看按钮是否应该被激活。这是我尝试过的：

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" />

代码背后：

    initialPlayerNameChoice.Attributes.Add("onkeyup", "javascript:validatePlayerName()");
    initialUpperLimitChoice.Attributes.Add("onkeyup", "javascript:validateUpperLimit()");
4

1 回答 1

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你几乎明白了。您只需要在代码中修复几行：

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有一个validate()函数，并且让两个字段都调用它onkeyup。如果您更改验证函数以返回 true 或 false，那么您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;
}

然后代替您的onkeyup代码（我认为您不需要该javascript:部分，但我不完全确定，因此如果它向您吠叫，只需将其放回原处）：

initialPlayerNameChoice.Attributes.Add("onkeyup", "validate()");
initialUpperLimitChoice.Attributes.Add("onkeyup", "validate()");
于 2012-11-15T19:44:40.220 回答