How do I copy to the clipboard in JavaScript?

What is the best way to copy text to the clipboard (multi-browser)?

I have tried:

function copyToClipboard(text) {
    if (window.clipboardData) { // Internet Explorer
        window.clipboardData.setData("Text", text);
    } else {
        unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
        const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);
        clipboardHelper.copyString(text);
    }
}

But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined.

A nice trick without using Flash: How does Trello access the user's clipboard?

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Best Answer-推荐答案

Overview

There are three primary browser APIs for copying to the clipboard:

1. 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.

2. document.execCommand('copy') (deprecated)