SelectAll and Copy Element text to Clipboard

//SELECTALL AND COPY ELEMENT TEXT TO CLIPBOARD
var SELECTOR = '.w3-code';
var html_button = '<button type="button" class="btn_copy_code">Copy code to clipboard</button>';
//$(SELECTOR).parent().append(html_button);
$(SELECTOR).after(html_button);

$('.btn_copy_code').click(function() {
    var selector = $(SELECTOR);
    //selectAll(selector);
    // Get selector index https://stackoverflow.com/questions/3578461/jquery-returning-the-number-eq-of-a-clicked-div?rq=1
    var index = $(this).index('.btn_copy_code');
    //console.log(index);
    //console.log(selector[index]);
    CopyToClipboard(selector[index]);
    $(this).eq(0).html("Copied");
});

$(SELECTOR).on('mouseup', function() {
    var sel, range;
    var el = $(this)[0];
    console.log($(this));
    if (window.getSelection && document.createRange) { //Browser compatibility
      sel = window.getSelection();
      if(sel.toString() == ''){ //no text selection
         window.setTimeout(function(){
            range = document.createRange(); //range object
            range.selectNodeContents(el); //sets Range
            sel.removeAllRanges(); //remove all ranges from selection
            sel.addRange(range);//add Range to a Selection.
        },1);
      }
    }else if (document.selection) { //older ie
        sel = document.selection.createRange();
        if(sel.text == ''){ //no text selection
            range = document.body.createTextRange();//Creates TextRange object
            range.moveToElementText(el);//sets Range
            range.select(); //make selection.
        }
    }
});

function selectAll(selector) {
    var sel, range;
    var el = selector[0];
    console.log(selector);
    if (window.getSelection && document.createRange) { //Browser compatibility
      sel = window.getSelection();
      if(sel.toString() == ''){ //no text selection
         window.setTimeout(function(){
            range = document.createRange(); //range object
            range.selectNodeContents(el); //sets Range
            sel.removeAllRanges(); //remove all ranges from selection
            sel.addRange(range);//add Range to a Selection.
        },1);
      }
    }else if (document.selection) { //older ie
        sel = document.selection.createRange();
        if(sel.text == ''){ //no text selection
            range = document.body.createTextRange();//Creates TextRange object
            range.moveToElementText(el);//sets Range
            range.select(); //make selection.
        }
    }
}

function CopyToClipboard(element) {
    //console.log(element);
  if (document.selection) {
    var range = document.body.createTextRange();
    range.moveToElementText(element);
    range.select().createTextRange();
    document.execCommand("copy");
  } else if (window.getSelection) {
    var range = document.createRange();
    range.selectNode(element);
    //remove all ranges https://stackoverflow.com/questions/51234160/javascript-copy-to-clipboard-works-only-once
    window.getSelection().removeAllRanges();
    window.getSelection().addRange(range);
    document.execCommand("copy");
    //alert("Text has been copied, now paste in the text-area")
  }
}