检查是否加载了元素，尽管Id存在，但document.getElementById仍然无效

Question

document.getElementById is not working.，但我可以看到DOM中存在id="calendar1_dayId2017-07-17"，即表：

<td class="dayNumber" id="calendar1_dayId2017-07-17"> <span class="otherDate">17</span> <span class="date" hidden="">2017-07-17</span></td>

$( document ).ready( function() {  
  <...>
  var day_Id = "calendar1_dayId2017-07-17"; 
  someFnc.prototype.getId = function(day_Id) {  
        <...>
        var tempInstFnc = function () { 
            console.log('in tempInstFnc'); 
        } 

      var loadTemp = new loadElemProt( day_Id, tempInstFnc );
      loadTemp.checkLoadInt = window.setInterval( function() { 
            loadTemp.checkLoadFnc(); }, 1000 ); 

      var temp = document.getElementById( "calendar1_dayId2017-07-17" )
      console.log('temp=');   console.log(temp); // null
  } //someFnc.prototype.getId = function(day_Id) { 

 }); //$( document ).ready(function() {  

下面是帮助我在上面的代码之前加载的函数 他们永远不会完成，console.log('startedFnc loadElemProt.checkLoadFnc'); //logs forever

var loadElemProt = function ( elemId, userFnc ) {
    console.log('STARTED loadElemProt constructor  elemId='+elemId )
    this.elemId = elemId; 
    this.userFnc = userFnc;
}; //  var loadElemProt = function () {

loadElemProt.prototype.checkLoadFnc = function() {
    console.log('startedFnc loadElemProt.checkLoadFnc'); //logs forever
    if(document.getElementById(this.elemId)) { this.stopIntervalFnc(); }
}; //loadElemProt.prototype.checkLoadFnc = function() {

loadElemProt.prototype.stopIntervalFnc = function() {
    console.log('startedFnc loadElemProt.stopIntervalFnc');
    clearInterval(this.checkLoadInt);
    this.callUserFnc();
}   // loadElemProt.prototype.stopIntervalFnc = function() {

loadElemProt.prototype.callUserFnc = function() {
    this.userFnc.call( null )
}