Javascript <return>：undefined

Question

我正在尝试使用Javascript将canvas放入iframe元素，但是当我执行代码时，我得到了：debuger中的undefined 这个代码可以有人帮助我吗？

function submitTryit() {
    var ifr = document.createElement("iframe");
    ifr.setAttribute("id", "iframeResult");
    document.getElementById("iframewrapper").innerHTML = "";
    document.getElementById("iframewrapper").appendChild(ifr);

    canvas();
}

function canvas(){
    var ifrr = document.getElementById("iframeResult");
    var iframediv = (ifrr.contentWindow.document || ifrr.contentDocument.document);
    var canv = document.createElement('canvas');
    canv.setAttribute("id", "mycanvas");
    iframediv.body.appendChild(canv);
}

Answer 1

你的所有代码都很好，问题是你太快运行了;您尝试在页面上存在之前获取touch。解决方案很简单，在确定页面已加载

之前不要调用iframewrapper

submitTryIt()

window.onload = function()
{
  submitTryit();
}

window.onload = function() {
  submitTryit();
}

function submitTryit() {
  var ifr = document.createElement("iframe");
  ifr.setAttribute("id", "iframeResult");
  document.getElementById("iframewrapper").innerHTML = "";
  document.getElementById("iframewrapper").appendChild(ifr);

  canvas();
}

function canvas() {
  var ifrr = document.getElementById("iframeResult");
  var iframediv = (ifrr.contentWindow.document || ifrr.contentDocument.document);
  var canv = document.createElement('canvas');
  canv.setAttribute("id", "mycanvas");
  iframediv.body.appendChild(canv);
}