The accepted answer does not work when you have multiple items to copy, and each with a separate "copy to clipboard" button. After clicking one button, the others will not work.
To make them work, I added some code to the accepted answer's function to clear text selections before doing a new one:
function CopyToClipboard(containerid) {
if (window.getSelection) {
if (window.getSelection().empty) { // Chrome
window.getSelection().empty();
} else if (window.getSelection().removeAllRanges) { // Firefox
window.getSelection().removeAllRanges();
}
} else if (document.selection) { // IE?
document.selection.empty();
}
if (document.selection) {
var range = document.body.createTextRange();
range.moveToElementText(document.getElementById(containerid));
range.select().createTextRange();
document.execCommand("copy");
} else if (window.getSelection) {
var range = document.createRange();
range.selectNode(document.getElementById(containerid));
window.getSelection().addRange(range);
document.execCommand("copy");
}
}