Copy to Clipboard in Chrome Extension

I'm making an extension for Google Chrome and I have hit a snag.

I need to copy a readonly textarea's content to the clipboard on click in the popup. Does anyone know the best way to go about this with pure Javascript and no Flash? I also have jQuery loaded in the extension, if that helps any. My current (non-working) code is...

function copyHTMLCB() {
$('#lb_html').select();
$('#lb_html').focus();
textRange = document.lb_html_frm.lb_html.createTextRange();
textRange.execCommand("RemoveFormat");
textRange.execCommand("Copy");
alert("HTML has been copied to your clipboard."); }

Answers:

Answer

You can copy to clipboard using Experimental Clipboard API, but it is available only in the dev branch of a browser and not enabled by default (more info)..

Answer

I found that the following works best, as it lets you specify the MIME type of the copied data:

copy: function(str, mimeType) {
  document.oncopy = function(event) {
    event.clipboardData.setData(mimeType, str);
    event.preventDefault();
  };
  document.execCommand("copy", false, null);
}
Answer

You can't copy a read only bit of text using execCommand("Copy"), it has to be an editable text area. The solution is to create a text input element and copy the text from there. Unfortunately you can't hide that element using display: none or visibility: hidden as that will also stop the select/copy command from working. However, you can 'hide' it using negative margins. Here's what I did in a Chrome Extension popup that obtains a short url. This is the bit of the code that re-writes the popup window with the shorturl (quick and dirty approach ;-)):

document.body.innerHTML = '<p><a href="'+shortlink+'" target="_blank" >'+shortlink+'</a><form style="margin-top: -35px; margin-left: -500px;"><input type="text" id="shortlink" value="'+shortlink+'"></form></p>'
document.getElementById("shortlink").select()
document.execCommand("Copy") 
Answer

I read somewhere that there are security restrictions with Javascript that stops you from interacting with the OS. I've had good success with ZeroClipboard in the past (http://code.google.com/p/zeroclipboard/), but it does use Flash. The Bitly website uses it quite effectively: http://bit.ly/

Answer

All credit goes to joelpt, but in case anyone else needs this to work in pure javascript without jQuery (I did), here's an adaptation of his solution:

function copyTextToClipboard(text) {
  //Create a textbox field where we can insert text to. 
  var copyFrom = document.createElement("textarea");

  //Set the text content to be the text you wished to copy.
  copyFrom.textContent = text;

  //Append the textbox field into the body as a child. 
  //"execCommand()" only works when there exists selected text, and the text is inside 
  //document.body (meaning the text is part of a valid rendered HTML element).
  document.body.appendChild(copyFrom);

  //Select all the text!
  copyFrom.select();

  //Execute command
  document.execCommand('copy');

  //(Optional) De-select the text using blur(). 
  copyFrom.blur();

  //Remove the textbox field from the document.body, so no other JavaScript nor 
  //other elements can get access to this.
  document.body.removeChild(copyFrom);
}
Answer

I'm using this simple function to copy any given plaintext to the clipboard (Chrome only, uses jQuery):

// Copy provided text to the clipboard.
function copyTextToClipboard(text) {
    var copyFrom = $('<textarea/>');
    copyFrom.text(text);
    $('body').append(copyFrom);
    copyFrom.select();
    document.execCommand('copy');
    copyFrom.remove();
}

// Usage example
copyTextToClipboard('This text will be copied to the clipboard.');

Due to the fast append-select-copy-remove sequence, it doesn't seem to be necessary to hide the textarea or give it any particular CSS/attributes. At least on my machine, Chrome doesn't even render it to screen before it's removed, even with very large chunks of text.

Note that this will only work within a Chrome extension/app. If you're using a v2 manifest.json you should declare the 'clipboardWrite' permission there; this is mandatory for apps and recommended for extensions.

Answer

I had a similar problem where I had to copy text from an element using only javascript. I'll add the solution to that problem here for anyone interested. This solution works for many HTML elements, including textarea.

HTML:

    <textarea id="text-to-copy">This is the text I want to copy</textarea>
    <span id="span-text-to-copy">This is the text I want to copy</span>

Javascript:

let textElement = document.getElementById("text-to-copy");

//remove selection of text before copying. We can also call this after copying
window.getSelection().removeAllRanges();

//create a Range object
let range = document.createRange();

//set the Range to contain a text node.
range.selectNode(textElement);

//Select the text node
window.getSelection().addRange(range);

try {
    //copy text
    document.execCommand('copy');
} catch(err) {
    console.log("Not able to copy ");
}

Note that if you wanted to copy a span element for instance, then you could get its text node and use it as a parameter for range.selectNode() to select that text:

let elementSpan = document.getElementById("span-text-to-copy");
let textNode = elementSpan.childNodes[0];
Answer

The Clipboard API is now supported by Chrome, and is designed to replace document.execCommand.

From MDN:

navigator.clipboard.writeText(text).then(() => {
    //clipboard successfully set
}, () => {
    //clipboard write failed, use fallback
});

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