从按钮值复制到剪贴板的问题

Question

请你看一下这个演示，让我知道为什么当我尝试从#coordinateX调用复制功能来读取按钮文本时，我无法复制#map值#coordinateX但代码适用于输入文本？ 如何才能使它能够读取按钮值？

(function() {

	'use strict';
  
  // click events
  document.body.addEventListener('click', copy, true);

	// event handler
	function copy(e) {

    // find target element

     var t = e.target;

      var c = t.dataset.copytarget;
      var inp = (c ? document.querySelector(c) : null);
      
    // is element selectable?
    if (inp && inp.select) {
      
      // select text
      inp.select();

      try {
        // copy text
        document.execCommand('copy');
        inp.blur();
        
        // copied animation
        t.classList.add('copied');
        setTimeout(function() { t.classList.remove('copied'); }, 1500);
      }
      catch (err) {
        alert('please press Ctrl/Cmd+C to copy');
      }
      
    }
    
	}

})();

http://www.sitepoint.com/

<div class="container">
<div class="btn-group">
  <button class="btn" id="coordinateX">49.124545</button>
  <button class="btn" id="map" data-copytarget="#coordinateX">Copy Coordinate</button>
</div>

<br />
  <label for="website">Website:</label>
<input type="text" id="txtCoordinateX" value="49.124545" />
<button data-copytarget="#txtCoordinateX">Copy Coordinate From Input</button>


</div>

Answer 1

<div class="container">
<div class="btn-group">
  <button class="btn" id="coordinateX">49.124545</button>
  <button class="btn" id="map" data-copytarget="#coordinateX">Copy Coordinate</button>
</div>

<br />
  <label for="website">Website:</label>
<input type="text" id="txtCoordinateX" value="49.124545" />
<button data-copytarget="#txtCoordinateX" id="copyBlock">Copy Coordinate From Input</button>

<span id="copyAnswer"></span>
</div>

var textarea = document.getElementById("txtCoordinateX");
var answer = document.getElementById("copyAnswer");
var copy   = document.getElementById("copyBlock");
copy.addEventListener('click', function(e) {

   // Select some text (you could also create a range)
   textarea.select(); 

   // Use try & catch for unsupported browser
   try {

       // The important part (copy selected text)
       var successful = document.execCommand('copy');

       if(successful) answer.innerHTML = 'Copied!';
       else answer.innerHTML = 'Unable to copy!';
   } catch (err) {
       answer.innerHTML = 'Unsupported Browser!';
   }
});

Fiddler https://jsfiddle.net/ktgzujLe/