javascript - 在 insertAdjacentHTML 之前声明一个空元素

Question

您好，我有一个简单的问题，我是否需要指定lblWelcomeUserMessage.innerHTML = ""; (见下面的代码)在下面的函数之前insertAdjacentHTML就可以了？它实际上可以按原样工作而无需声明，但我想知道最佳方法是什么？

// Dynamic HTML / user interface for ALL users
  function showWelcomeMessage() {

      //lblWelcomeUserMessage.innerHTML = "";

      var sWelcomeUserMessage = '<h3>' + 'Welcome:' + '  ' + sessionStorage.getItem( 'name' ) + 
      '  ' +  sessionStorage.getItem( 'lastname' ) + '  ' + sessionStorage.getItem( 'role' ) + ' </h3>';
      var iUserImage = '<img src=" ' + sessionStorage.getItem( 'image' ) + ' " width="50px">';
      lblWelcomeUserMessage.insertAdjacentHTML( 'beforeend', sWelcomeUserMessage + iUserImage );
  }

Answer 1

这取决于你想做什么。

If you are calling showWelcomeMessage function more than once then you need to set it to empty lblWelcomeUserMessage.innerHTML = ""

       function showWelcomeMessage() {

  lblWelcomeUserMessage.innerHTML = "";

   var sWelcomeUserMessage = '<h3>' + 'Welcome:' + '  ' + sessionStorage.getItem( 'name' ) + 
  '  ' +  sessionStorage.getItem( 'lastname' ) + '  ' + sessionStorage.getItem( 'role' ) + ' </h3>';
  var iUserImage = '<img src=" ' + sessionStorage.getItem( 'image' ) + ' " width="50px">';
  lblWelcomeUserMessage.insertAdjacentHTML( 'beforeend', sWelcomeUserMessage + iUserImage );
  }

   setInterval(showWelcomeMessage,4000);

或者

Otherwise you can remove lblWelcomeUserMessage.innerHTML = ""; from above code