onFocus和onBlur [英] onFocus and onBlur

问题描述

出于某种原因，onblur和onfocus属性不起作用。我是否正确定义它们？

For some reason the onblur and onfocus properties don't work. Am I defining them right?

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;};

我也试过把function（）{if（replyTxt.value） == replyTxt.defaultValue）replyTxt.value ='';} in quotations

I have also tried putting "function(){if(replyTxt.value==replyTxt.defaultValue) replyTxt.value='';}" in quotations

推荐答案

事件有效 - 所以你的逻辑可能有问题......

The events work - so there may be a problem with your logic...

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......

Where do you set replyTxt.defaultValue? In your example, you don't - so the logic will never fire. Try this...

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;};

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