function getIframeText() { var iframe0 = document.getElementById("checkout-iframe"); var iframe0document=iframe0.contentDocument||iframe0.contentWindow.document; var inputIframe = iframe0document.getElementById("wc-first-data-payeezy-gateway-credit-card-account-number"); alert(inputIframe.value); }
document.getElementById('place_order').onclick = getIframeText() { alert('you clicked me'); }