html

<script src="https://cdn.staticfile.org/qrcodejs/1.0.0/qrcode.min.js"></script>
<textarea   placeholder="文本框"   id="kw"></textarea>
<button onclick="ewm()">生成二维码</button>

<div id="erwm">
    <div id="qrcode"></div>
    <div id="buttons"></div>
    </div>

JavaScript

function ewm() {
  var kw = document.getElementById("kw").value;
    var qrcodeDiv = document.getElementById("qrcode");
    var buttonsDiv = document.getElementById("buttons");
  
  
    if (kw.trim() === "") {
      alert("请在“内容框”输入内容,文字，链接等");
      return;
    }else if (/[-\u4E00-\u9FA5]/.test(kw) && kw.indexOf('-') !== -1) {
    var wwww = encodeURIComponent(kw);
  } else {
    var wwww = kw;
  }
  
  
  
    
    
      qrcodeDiv.innerHTML = "";
      buttonsDiv.innerHTML = "";
    
  document.getElementById('erwm').style.display = 'block';
    var qrcode = new QRCode(qrcodeDiv, {
      text: wwww,
      width: 400,
      height: 400
    });
    
  
    var downloadBtn = document.createElement("a");
    downloadBtn.href = qrcodeDiv.firstChild.toDataURL();
    downloadBtn.download = "二维码.png";
    downloadBtn.innerHTML = "下载二维码";
    downloadBtn.id = "xiazai";
  
  
    var closeBtn = document.createElement("a");
    closeBtn.innerHTML = "关闭二维码";
  closeBtn.id = "guangb";
  closeBtn.onclick = function() {
    qrcodeDiv.innerHTML = "";
    buttonsDiv.innerHTML = "";
    
    document.getElementById('erwm').style.display = 'none';
  };

  buttonsDiv.appendChild(downloadBtn);
  buttonsDiv.appendChild(closeBtn);
};