How to Use js to determine whether dom has a class value?

How to Use js to determine whether dom has a class value?

For example:

Determine whether the class of an html node has no-js.
1. jquery Implementation Method
$("html").hasClass('no-js');
Implementation of jquery source code:
var rclass = /[\t\r\n\f]/g;jQuery.fn.extend({ hasClass: function(selector) {  var className = " " + selector + " ",   i = 0,   l = this.length;  for (; i < l; i++) {   if (this[i].nodeType === 1 &&    (" " + this[i].className + " ").replace(rclass, " ").indexOf(className) > -1) {    return true;   }  }  return false; }})
2. js Implementation Method
function hasClass(element, cls) { return (' ' + element.className + ' ').indexOf(' ' + cls + ' ') > -1;}hasClass(document.querySelector("html"), 'no-js');
3. H5 classList
Note:

 
 
 
  
The indexOf method of the string cannot distinguish classes such as. no-js and. no-js-indeed;
 
 
  
The separator of the class name may not be a space or \ t.

 
Code:
var hasClass = (function(){ var div = document.createElement("div") ; if( "classList" in div && typeof div.classList.contains === "function" ) {  return function(elem, className){   return elem.classList.contains(className) ;  } ; } else {  return function(elem, className){   var classes = elem.className.split(/\s+/) ;   for(var i= 0 ; i < classes.length ; i ++) {    if( classes[i] === className ) {     return true ;    }   }   return false ;  } ; }})() ;alert( hasClass(document.documentElement, "no-js") ) ;
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