An example of how synthetic click-to-"copy" events might look if we use `document.execCommand`.

clickToCopy_queryCommand.js

var hasModernClipboardApi, queryCopySupported, syntheticCopySupported, button;


hasModernClipboardApi = window.ClipboardEvent != null;

try {
  queryCopySupported = document.queryCommandSupported("click-to-copy") === true;
}
catch (e) {
  queryCopySupported = false;
}

syntheticCopySupported = hasModernClipboardApi && queryCopySupported;

button = document.getElementById("copyButton");

if (!syntheticCopySupported) {

  //
  // Polyfill in with Flash clipboard support or the weakly supported RichTextEditor and/or oldIE Clipboard APIs
  //

  // e.g.
  var client = new ZeroClipboard(button);
  client.on("ready", function() {
    client.on("copy", function(e) {
      e.clipboardData.setData("text/plain", "WINNING! With Flash...");
      //e.preventDefault();
    });
  });

}
else {

  button.addEventListener("click", function(e) {
    var isClickEvent,
        queryCopyEnabled,
        syntheticCopyEnabledRightNow,
        syntheticCopySucceeded;

    isClickEvent = e != null && e.type === "click";

    try {
      queryCopyEnabled = document.queryCommandEnabled("click-to-copy") === true;
    }
    catch (e) {
      queryCopyEnabled = false;
    }

    syntheticCopyEnabledRightNow = isModernCopyEvent && queryCopyEnabled;

    if (syntheticCopyEnabledRightNow) {
      try {
        // Trigger the copy action
        syntheticCopySucceeded = document.execCommand("copy", false, null);
      }
      catch (e) {
        syntheticCopySucceeded = false;
      }
    }
    else {
      syntheticCopySucceeded = false;
    }

    // Announce the results
    console.log("Click-to-copy was " + (syntheticCopySucceeded ? "NOT " : "") + "successful");

  }, false);


  button.addEventListener("copy", function(e) {
    if (e != null && e.clipboardData && e.clipboardData.setData) {
      e.clipboardData.setData("text/plain", "WINNING! With HTML.");
      e.preventDefault();
    }
    else {
      console.error("Unexpected error! This was not a modern ClipboardEvent instance.");
    }
  }, false);

}