Copying text of textarea in clipboard when button is clicked

You need to use select() to selecting text of textarea and use execCommand('copy') to coping selected text. Its work in upper version of browsers.

$("button").click(function(){
    $("textarea").select();
    document.execCommand('copy');
});

Also you can do this work without jquery as shown in bottom

document.querySelector("button").onclick = function(){
    document.querySelector("textarea").select();
    document.execCommand('copy');
}

document.querySelector("button").onclick = function(){
  document.querySelector("textarea").select();
  document.execCommand('copy');
};

<button>Select</button>
<br/>
<textarea></textarea>