utils.js

// partially borrowed from clipboard.js
// Must call it from a click event handler
// returns true if the text was copied, false otherwise

function copyToClipboard(text) {
    const isRTL = document.documentElement.getAttribute('dir') == 'rtl';
    const fakeElem = document.createElement('textarea');
    let success = true;

    // Prevent zooming on iOS
    fakeElem.style.fontSize = '12pt';
    // Reset box model
    fakeElem.style.border = '0';
    fakeElem.style.padding = '0';
    fakeElem.style.margin = '0';
    // Move element out of screen horizontally
    fakeElem.style.position = 'absolute';
    fakeElem.style[ isRTL ? 'right' : 'left' ] = '-9999px';
    // Move element to the same position vertically
    fakeElem.style.top = (window.pageYOffset || document.documentElement.scrollTop) + 'px';
    fakeElem.setAttribute('readonly', '');
    fakeElem.value = text;
    // Add element to the body
    document.body.appendChild(fakeElem);
    // Select the element
    fakeElem.select();
    // Copy to clipboard
    try {
        document.execCommand('copy');
    } catch(e) {
        success = false;
    }
    // De-select the element
    fakeElem.blur();
    // Remove from body
    document.body.removeChild(fakeElem);

    return success;
}