Question

出于某种原因，onblur和onfocus属性不起作用。我定义它们了吗？

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;};

我也尝试将"function(){if(replyTxt.value==replyTxt.defaultValue) replyTxt.value='';}"放入引号

Answer 1

事件有效 - 因此您的逻辑可能存在问题......

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

你在哪里设置replyTxt.defaultValue？在你的例子中，你没有 - 所以逻辑永远不会触发。试试这个......

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：尝试在事件功能中将replyTxt替换为this。

Answer 3

尝试setAttribute。有关函数的更多信息，请查看此link

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物上。

<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

实际上我正在研究一个类似的问题作为家庭作业，我发现一旦鼠标落在田地上就更好地清除田地，而不是做一个比较，如果保持不变，然后清除它。

onFocus和onBlur

5 个答案: