javascript check if element has class

if(document.getElementById("myElmentID").classList.contains("hidden")){
// I have the 'hidden' class
}const element = document.querySelector("#box");

element.classList.contains("active");element.classList.contains(class);//How to check if class attribute contains something?
//https://stackoverflow.com/questions/34992613/how-to-check-if-class-attribute-contains-something
//el is the web element
if(el.getAttribute("class").split(" ").contains("disabled"))
{  
    //your code
}

or 

#region HTML Method
public static bool hasClass(WebControl element, string strClass)
{
  return Convert.ToString(element.Attributes["class"]).Split(' ').Contains(strClass);
}
#endregionfunction whatIsInAName(collection, source) {
  // "What's in a name? that which we call a rose
  // By any other name would smell as sweet.”
  // -- by William Shakespeare, Romeo and Juliet
  var srcKeys = Object.keys(source);

  return collection.filter(function(obj) {
    return srcKeys.every(function(key) {
      return obj.hasOwnProperty(key) && obj[key] === source[key];
    });
  });
}

// test here
whatIsInAName(
  [
    { first: "Romeo", last: "Montague" },
    { first: "Mercutio", last: null },
    { first: "Tybalt", last: "Capulet" }
  ],
  { last: "Capulet" }
);<div id="box" class="active"></div>