javascript - onFocus 和 onBlur

Question

由于某种原因，onblurandonfocus属性不起作用。我对它们的定义正确吗？

var replyTxt = document.createElement("input");
    replyTxt.id="replyTxt";
    replyTxt.type="text";
    replyTxt.value="Write a reply";
    
    replyTxt.onfocus = function(){if(replyTxt.value==replyTxt.defaultValue) replyTxt.value='';};
    replyTxt.onblur= function(){if(replyTxt.value=='') replyTxt.value=replyTxt.defaultValue;};

我也尝试"function(){if(replyTxt.value==replyTxt.defaultValue) replyTxt.value='';}"过引用

Answer 1

事件有效 - 所以你的逻辑可能有问题......

if(replyTxt.value==replyTxt.defaultValue) replyTxt.value='';

你在哪里设置replyTxt.defaultValue？在您的示例中，您没有 - 所以逻辑永远不会触发。尝试这个...

var replyTxtDefaultText = "Write a reply";
var replyTxt = document.createElement("input");
    replyTxt.id="replyTxt";
    replyTxt.type="text";
    replyTxt.value=replyTxtDefaultText;

    replyTxt.onfocus = function(){if(replyTxt.value==replyTxtDefaultText) replyTxt.value='';};
    replyTxt.onblur= function(){if(replyTxt.value=='') replyTxt.value=replyTxtDefaultText;};

Answer 2

只是一个提示：尝试在您的事件函数中替换replyTxt为。this

Answer 3

试试setAttribute。有关功能的更多信息，请查看此链接

var replyTxt = document.createElement("input");
replyTxt.setAttribute('onFocus', 'focusFunction()');

function focusFunction()
{
   if(replyTxt.value==replyTxtDefaultText) 
      replyTxt.value='';
}

Answer 4

并确保将其附加到某些东西上。

<form id="x">
</form>
<script>
window.onload=function() {
  var replyTxt = document.createElement("input");
  replyTxt.id="replyTxt";
  replyTxt.type="text";
  replyTxt.value=replyTxt.defaultValue="Write a reply";
  replyTxt.onfocus = function(){if(this.value==this.defaultValue) this.value='';};
  replyTxt.onblur= function(){if(this.value=='') this.value=this.defaultValue;};

  document.getElementById('x').appendChild(replyTxt);
}
</script>

Answer 5

实际上，我正在处理与家庭作业类似的问题，我发现最好在鼠标落在场地上时立即清除场地，而不是在未触及的情况下进行比较然后清除它。