You can copy text to the clipboard in most browsers because most browsers have the ability to programmatically copy a selection of text to the clipboard using document.execCommand("copy") that works off a selection.
As with the other actions in a browser (like opening a new window), then copy to the clipboard can only be done via a specific user action (like a mouse click). For example, it cannot be done via a timer.
You can follow this example:
document.getElementById("copyButton").addEventListener("click", function() {
copyToClipboard(document.getElementById("copyTarget"));
});
function copyToClipboard(elem) {
// create hidden text element, if it doesn't already exist
var targetId = "_hiddenCopyText_";
var isInput = elem.tagName === "INPUT" || elem.tagName === "TEXTAREA";
var origSelectionStart, origSelectionEnd;
if (isInput) {
// can just use the original source element for the selection and copy
target = elem;
origSelectionStart = elem.selectionStart;
origSelectionEnd = elem.selectionEnd;
} else {
// must use a temporary form element for the selection and copy
target = document.getElementById(targetId);
if (!target) {
var target = document.createElement("textarea");
target.style.position = "absolute";
target.style.left = "-9999px";
target.style.top = "0";
target.id = targetId;
document.body.appendChild(target);
}
target.textContent = elem.textContent;
}
// select the content
var currentFocus = document.activeElement;
target.focus();
target.setSelectionRange(0, target.value.length);
// copy the selection
var succeed;
try {
succeed = document.execCommand("copy");
} catch(e) {
succeed = false;
}
// restore original focus
if (currentFocus && typeof currentFocus.focus === "function") {
currentFocus.focus();
}
if (isInput) {
// restore prior selection
elem.setSelectionRange(origSelectionStart, origSelectionEnd);
} else {
// clear temporary content
target.textContent = "";
}
return succeed;
}
input {
width: 400px;
}
<input type="text" id="copyTarget" value="Text to Copy"> <button id="copyButton">Copy</button><br><br>
<input type="text" placeholder="Click here and press Ctrl-V to see clipboard contents">
Here's a little more advanced demo: https://jsfiddle.net/jfriend00/v9g1x0o6/
And, you can also get a pre-built library that does this for you with clipboard.js.
If you are directly copying to the clipboard via JavaScript it'll not be permitted by any modern browser for security reasons. You can just use the Flash capability for copying to the clipboard that can only be triggered by a direct user click.
As mentioned already, ZeroClipboard is a popular set of code for managing the Flash object to do the copy. I've used it. If Flash is installed on the browsing device (which rules out mobile or tablet), it will work.
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