function copyToClipboard() {
    var textBox = document.getElementById("myvalue");
    textBox.select();
    document.execCommand("copy");
}

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如果要将输入文本复制到剪贴板，请执行代码。

//HTML
<input type="text" class="form-control" name="myvalue"  id="myvalue" value="YEAH" readonly  />
<button class="btn btn-primary btn-block" onclick="copyToClipboard();">Copy myvalue</button>

//SCRIPT For ClipBoard Copy
 <Script>
    function copyToClipboard() {
        var textBox = document.getElementById("myvalue");
        textBox.select();
        document.execCommand("copy");
    }
</Script>


//For local storage variable copy
<Script>
    function copyToStorage() {
        var textBox = document.getElementById("myvalue");
        if(typeof(Storage) !== "undefined") {

            var textBox_value=textBox.value;
            localStorage.setItem("textBox_value", textBox_value);
         } else {
               alert("Sorry your browser does not support this script");
           }
    }
</Script>

   // Also there one to use an element like hidden to store the value for same page life.

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document.execCommand（）现在已经过时了，替代方法是通过navigator.clipboard使用API API。根据MDN Web服务器（https://developer.mozilla.org/en-US/docs/Web/API/Clipboard_API）：

function copyToClipboard() {
  var textBox = document.getElementById("myvalue");
  console.log(textBox.value)
  navigator.clipboard.writeText(textBox.value);
}

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