How to check if an element has multiple classes with vanilla JS

Question

I'm trying to figure out how to write an if statement that works something like this:

if (element contains class 1 && class 2) {
   // do this
}

How do I write that if statement to check for multiple classes?

Is there a way to make the .contains method check for more than one class?

What I've found so far:

How to check class of multiple class elements in javascript, without jquery

Problem is, it seems to be returning an array of all the classes that the element contains, which is not what I want. I need the function to check if the element contains the classes that I am supplying it with.

One of the solutions looks to me like it's asking us to create our own function to do this, but is there a native method on JS which will do the trick?

I'm quite new to this stuff and I really appreciate the patience you guys have shown in answering my questions.

Answer 1

Put the class names you want to test for into an array, then use Array.prototype.every() to check if all members of your array exist in the element's classList:

console.log(['a', 'b'].every(e=>div.classList.contains(e)))
console.log(['a', 'b', 'c'].every(e=>div.classList.contains(e)))

<div class="a b" id="div"></div>

Unfortunately Element.classList is read-only, so you cannot add anything to its prototype. You can however do that on the Array.prototype:

Array.prototype.contains = function(...args) { 
  return [...args].every(c=>this.includes(c))
}

console.log([...div.classList].contains('a', 'b'))
console.log([...div.classList].contains('a', 'c'))
console.log([...div.classList].contains('a', 'c.d'))

<div class="a b c.d" id="div"></div>

Important: Please note that this violates the basic OOP rule Do not modify objects you don't own. As such, it would be better to create a named function taking the element and an array with a list of classes to test for.

Answer 2

You can use the .matches() API on the element, and it's pretty well-supported now:

if (element.matches(".class1.class2")) ...

It's like a built-in version of jQuery .is().

Documentation link.