if classlist has class code example

Example 1: javascript hasclass

if (document.body.classList.contains('thatClass')) {
    // do some stuff
}

Example 2: js check for class in classList

element.classList.contains(className);

Example 3: javascript hass class

if (myElement.classList.contains('someClassname')) {
    // do something
}

Example 4: if classlist contains js

element.classList.contains(class);