Simple Implementation of Obtaining class in javascript

There is no way to get class in js, and I have found some encapsulated methods, so I will sort them out here

(1) Package first

// Encapsulation getClass 
      function getClass(tagName,className) // Get the label name tagName, Class name className Elements of  
      { 
        if(document.getElementsByClassName) // Support this function  
        {    return document.getElementsByClassName(className); 
        } 
        else 
        {    var tags=document.getElementsByTagName(tagName);// Get Label  
          var tagArr=[];// Used to return a class named className Elements of  
          for(var i=0;i < tags.length; i++) 
          { 
            if(tags[i].class == className) 
            { 
              tagArr[tagArr.length] = tags[i];// Save the elements that meet the conditions  
            } 
          } 
          return tagArr; 
        } 
      } 

(2) Subject program

<ul>
  <li class="dicTap">1</li>
  <li class="dicTap">2</li>
  <li class="dicTap">3</li>
  <li class="dicTap">4</li>
</ul>     

(3) Obtain all li content programs whose class is dicTap

window.onload = function()
{  var topMenus = getClass('li','dicTap');
  for(var i=0;i < topMenus.length; i++)
  {
    alert(topMenus[i].innerHTML);    
  }

}

(4) Practical application in the project

// Clicked    Custom properties personid Open the Details page and cross-page value transfer  
      var dicTap = getClass('li','dicTap'); 
        for(var i=0;i <dicTap.length; i++) 
        { 
          dicTap[i].addEventListener('tap',function(){ 
            var personId=this.getAttribute("personid"); 
            localStorage.a=personId; 
            mui.openWindow({ 
            url: 'disciplineDetail.html', 
            id:'disciplineDetail' 
            }); 
          }) 
        } 
 
      // Encapsulation getClass 
      function getClass(tagName,className) // Get the label name tagName, Class name className Elements of  
      { 
        if(document.getElementsByClassName) // Support this function  
        {    return document.getElementsByClassName(className); 
        } 
        else 
        {    var tags=document.getElementsByTagName(tagName);// Get Label  
          var tagArr=[];// Used to return a class named className Elements of  
          for(var i=0;i < tags.length; i++) 
          { 
            if(tags[i].class == className) 
            { 
              tagArr[tagArr.length] = tags[i];// Save the elements that meet the conditions  
            } 
          } 
          return tagArr; 
        } 
      }