Overview
There are three primary browser APIs for copying to the clipboard:
Async Clipboard API [navigator.clipboard.writeText]
- Text-focused portion available in Chrome 66 (March 2018)
- Access is asynchronous and uses JavaScript Promises, can be written so security user prompts (if displayed) don't interrupt the JavaScript in the page.
- Text can be copied to the clipboard directly from a variable.
- Only supported on pages served over HTTPS.
- In Chrome 66 pages inactive tabs can write to the clipboard without a permissions prompt.
document.execCommand('copy')
(deprecated) 👎
- Most browsers support this as of ~April 2015 (see Browser Support below).
- Access is synchronous, i.e. stops JavaScript in the page until complete including displaying and user interacting with any security prompts.
- Text is read from the DOM and placed on the clipboard.
- During testing ~April 2015 only Internet Explorer was noted as displaying permissions prompts whilst writing to the clipboard.
Overriding the copy event
- See Clipboard API documentation on Overriding the copy event.
- Allows you to modify what appears on the clipboard from any copy event, can include other formats of data other than plain text.
- Not covered here as it doesn't directly answer the question.
General development notes
Don't expect clipboard related commands to work whilst you are testing code in the console. Generally, the page is required to be active (Async Clipboard API) or requires user interaction (e.g. a user click) to allow (document.execCommand('copy')
) to access the clipboard see below for more detail.
IMPORTANT (noted here 2020/02/20)
Note that since this post was originally written deprecation of permissions in cross-origin IFRAMEs and other IFRAME "sandboxing" prevents the embedded demos "Run code snippet" buttons and "codepen.io example" from working in some browsers (including Chrome and Microsoft Edge).
To develop create your own web page, serve that page over an HTTPS connection to test and develop against.
Here is a test/demo page which demonstrates the code working:
https://deanmarktaylor.github.io/clipboard-test/
Async + Fallback
Due to the level of browser support for the new Async Clipboard API, you will likely want to fall back to the document.execCommand('copy')
method to get good browser coverage.
Here is a simple example (may not work embedded in this site, read "important" note above):
function fallbackCopyTextToClipboard(text) {
var textArea = document.createElement("textarea");
textArea.value = text;
// Avoid scrolling to bottom
textArea.style.top = "0";
textArea.style.left = "0";
textArea.style.position = "fixed";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'successful' : 'unsuccessful';
console.log('Fallback: Copying text command was ' + msg);
} catch (err) {
console.error('Fallback: Oops, unable to copy', err);
}
document.body.removeChild(textArea);
}
function copyTextToClipboard(text) {
if (!navigator.clipboard) {
fallbackCopyTextToClipboard(text);
return;
}
navigator.clipboard.writeText(text).then(function() {
console.log('Async: Copying to clipboard was successful!');
}, function(err) {
console.error('Async: Could not copy text: ', err);
});
}
var copyBobBtn = document.querySelector('.js-copy-bob-btn'),
copyJaneBtn = document.querySelector('.js-copy-jane-btn');
copyBobBtn.addEventListener('click', function(event) {
copyTextToClipboard('Bob');
});
copyJaneBtn.addEventListener('click', function(event) {
copyTextToClipboard('Jane');
});
<div style="display:inline-block; vertical-align:top;">
<button class="js-copy-bob-btn">Set clipboard to BOB</button><br /><br />
<button class="js-copy-jane-btn">Set clipboard to JANE</button>
</div>
<div style="display:inline-block;">
<textarea class="js-test-textarea" cols="35" rows="4">Try pasting into here to see what you have on your clipboard:
</textarea>
</div>
(codepen.io example may not work, read "important" note above)
Note that this snippet is not working well in Stack Overflow's embedded preview you can try it here: https://codepen.io/DeanMarkTaylor/pen/RMRaJX?editors=1011
Async Clipboard API
Note that there is an ability to "request permission" and test for access to the clipboard via the permissions API in Chrome 66.
var text = "Example text to appear on clipboard";
navigator.clipboard.writeText(text).then(function() {
console.log('Async: Copying to clipboard was successful!');
}, function(err) {
console.error('Async: Could not copy text: ', err);
});
document.execCommand('copy')
The rest of this post goes into the nuances and detail of the document.execCommand('copy')
API.
Browser Support
The JavaScript document.execCommand('copy')
support has grown, see the links below for browser updates: (deprecated) 👎
Simple Example
(may not work embedded in this site, read "important" note above)
var copyTextareaBtn = document.querySelector('.js-textareacopybtn');
copyTextareaBtn.addEventListener('click', function(event) {
var copyTextarea = document.querySelector('.js-copytextarea');
copyTextarea.focus();
copyTextarea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'successful' : 'unsuccessful';
console.log('Copying text command was ' + msg);
} catch (err) {
console.log('Oops, unable to copy');
}
});
<p>
<button class="js-textareacopybtn" style="vertical-align:top;">Copy Textarea</button>
<textarea class="js-copytextarea">Hello I'm some text</textarea>
</p>
Complex Example: Copy to clipboard without displaying input
The above simple example works great if there is a textarea
or input
element visible on the screen.
In some cases, you might wish to copy text to the clipboard without displaying an input
/ textarea
element. This is one example of a way to work around this (basically insert an element, copy to clipboard, remove element):
Tested with Google Chrome 44, Firefox 42.0a1, and Internet Explorer 11.0.8600.17814.
(may not work embedded in this site, read "important" note above)
function copyTextToClipboard(text) {
var textArea = document.createElement("textarea");
//
// *** This styling is an extra step which is likely not required. ***
//
// Why is it here? To ensure:
// 1. the element is able to have focus and selection.
// 2. if the element was to flash render it has minimal visual impact.
// 3. less flakyness with selection and copying which **might** occur if
// the textarea element is not visible.
//
// The likelihood is the element won't even render, not even a
// flash, so some of these are just precautions. However in
// Internet Explorer the element is visible whilst the popup
// box asking the user for permission for the web page to
// copy to the clipboard.
//
// Place in the top-left corner of screen regardless of scroll position.
textArea.style.position = 'fixed';
textArea.style.top = 0;
textArea.style.left = 0;
// Ensure it has a small width and height. Setting to 1px / 1em
// doesn't work as this gives a negative w/h on some browsers.
textArea.style.width = '2em';
textArea.style.height = '2em';
// We don't need padding, reducing the size if it does flash render.
textArea.style.padding = 0;
// Clean up any borders.
textArea.style.border = 'none';
textArea.style.outline = 'none';
textArea.style.boxShadow = 'none';
// Avoid flash of the white box if rendered for any reason.
textArea.style.background = 'transparent';
textArea.value = text;
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'successful' : 'unsuccessful';
console.log('Copying text command was ' + msg);
} catch (err) {
console.log('Oops, unable to copy');
}
document.body.removeChild(textArea);
}
var copyBobBtn = document.querySelector('.js-copy-bob-btn'),
copyJaneBtn = document.querySelector('.js-copy-jane-btn');
copyBobBtn.addEventListener('click', function(event) {
copyTextToClipboard('Bob');
});
copyJaneBtn.addEventListener('click', function(event) {
copyTextToClipboard('Jane');
});
<div style="display:inline-block; vertical-align:top;">
<button class="js-copy-bob-btn">Set clipboard to BOB</button><br /><br />
<button class="js-copy-jane-btn">Set clipboard to JANE</button>
</div>
<div style="display:inline-block;">
<textarea class="js-test-textarea" cols="35" rows="4">Try pasting into here to see what you have on your clipboard:
</textarea>
</div>
Additional notes
Only works if the user takes an action
All document.execCommand('copy')
calls must take place as a direct result of a user action, e.g. click event handler. This is a measure to prevent messing with the user's clipboard when they don't expect it.
See the Google Developers post here for more info.
Clipboard API
Note the full Clipboard API draft specification can be found here:
https://w3c.github.io/clipboard-apis/
Is it supported?
document.queryCommandSupported('copy')
should return true
if the command "is supported by the browser".
- and
document.queryCommandEnabled('copy')
return true
if the document.execCommand('copy')
will succeed if called now. Checking to ensure the command was called from a user-initiated thread and other requirements are met.
However, as an example of browser compatibility issues, Google Chrome from ~April to ~October 2015 only returned true
from document.queryCommandSupported('copy')
if the command was called from a user-initiated thread.
Note compatibility detail below.
Browser Compatibility Detail
Whilst a simple call to document.execCommand('copy')
wrapped in a try
/catch
block called as a result of a user click will get you the most compatibility use the following has some provisos:
Any call to document.execCommand
, document.queryCommandSupported
or document.queryCommandEnabled
should be wrapped in a try
/catch
block.
Different browser implementations and browser versions throw differing types of exceptions when called instead of returning false
.
Different browser implementations are still in flux and the Clipboard API is still in draft, so remember to do your testing.
Best Answer
What you should know about
this
this
(aka "the context") is a special keyword inside each function and its value only depends on how the function was called, not how/when/where it was defined. It is not affected by lexical scopes like other variables (except for arrow functions, see below). Here are some examples:To learn more about
this
, have a look at the MDN documentation.How to refer to the correct
this
Use arrow functions
ECMAScript 6 introduced arrow functions, which can be thought of as lambda functions. They don't have their own
this
binding. Instead,this
is looked up in scope just like a normal variable. That means you don't have to call.bind
. That's not the only special behavior they have, please refer to the MDN documentation for more information.Don't use
this
You actually don't want to access
this
in particular, but the object it refers to. That's why an easy solution is to simply create a new variable that also refers to that object. The variable can have any name, but common ones areself
andthat
.Since
self
is a normal variable, it obeys lexical scope rules and is accessible inside the callback. This also has the advantage that you can access thethis
value of the callback itself.Explicitly set
this
of the callback - part 1It might look like you have no control over the value of
this
because its value is set automatically, but that is actually not the case.Every function has the method
.bind
[docs], which returns a new function withthis
bound to a value. The function has exactly the same behavior as the one you called.bind
on, only thatthis
was set by you. No matter how or when that function is called,this
will always refer to the passed value.In this case, we are binding the callback's
this
to the value ofMyConstructor
'sthis
.Note: When a binding context for jQuery, use
jQuery.proxy
[docs] instead. The reason to do this is so that you don't need to store the reference to the function when unbinding an event callback. jQuery handles that internally.Set
this
of the callback - part 2Some functions/methods which accept callbacks also accept a value to which the callback's
this
should refer to. This is basically the same as binding it yourself, but the function/method does it for you.Array#map
[docs] is such a method. Its signature is:The first argument is the callback and the second argument is the value
this
should refer to. Here is a contrived example:Note: Whether or not you can pass a value for
this
is usually mentioned in the documentation of that function/method. For example, jQuery's$.ajax
method [docs] describes an option calledcontext
:Common problem: Using object methods as callbacks/event handlers
Another common manifestation of this problem is when an object method is used as callback/event handler. Functions are first-class citizens in JavaScript and the term "method" is just a colloquial term for a function that is a value of an object property. But that function doesn't have a specific link to its "containing" object.
Consider the following example:
The function
this.method
is assigned as click event handler, but if thedocument.body
is clicked, the value logged will beundefined
, because inside the event handler,this
refers to thedocument.body
, not the instance ofFoo
.As already mentioned at the beginning, what
this
refers to depends on how the function is called, not how it is defined.If the code was like the following, it might be more obvious that the function doesn't have an implicit reference to the object:
The solution is the same as mentioned above: If available, use
.bind
to explicitly bindthis
to a specific valueor explicitly call the function as a "method" of the object, by using an anonymous function as callback / event handler and assign the object (
this
) to another variable:or use an arrow function: