4-11 Programming exercises (need to be optimized) – learn onblur and onfocus mouse events, based on the renderings, add code

Topic request

Thought analysis

Code implementation

<! DOCTYPEhtml>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
  <title>practice</title>
  <style>
    .red {
      border: 1px solid red;
    }
    .black {
      border: 1px solid # 000;
    }
  </style>
</head>

<body>Name:<input type="text" id="text"><span></span>
  <script>
    var text = document.getElementById('text');
    var tip = document.getElementsByTagName('span') [0];

    text.onfocus = function () {
      if (text.value.length == 0) {
        tip.innerText = 'Please enter your name';
      }

    }
    text.onblur = function () {
      if (text.value.length == 0) {
        tip.innerText = 'User name cannot be empty';
        text.className = 'red';
      } else {
        tip.innerText = ' ';
        text.className = 'black'; }}</script>
</body>

</html>
Copy the code

rendering

defects

Instead: added the class property black to do this