JavaScript：在多个元素上添加/删除单个类

Question

How can I add/remove a single class on multiple class-selected elements.

In my setup I have some variables cached for doesn't stuff to each:

var classOne    = document.querySelector(".class1");
var classTwo    = document.querySelector(".class2");
var classThree  = document.querySelector(".class3");
var classFour   = document.querySelector(".class4");

but I'm also trying to do something like this:

var allClasses = [classOne, classTwo, classThree, classFour];

allClasses.classList.add("active");
allClasses.classList.remove("active");

Doesn't seem to be working though.

No jQuery please.

Answer 1

Try this:

var classOne    = document.querySelector(".class1");
var classTwo    = document.querySelector(".class2");
var classThree  = document.querySelector(".class3");
var classFour   = document.querySelector(".class4");

var allClasses = [classOne, classTwo, classThree, classFour];

allClasses.forEach(function(el) {
  el.classList.add("active")
})

Answer 2

Now this can be simplified to:

document.querySelectorAll('.class1, .class2, .class3, .class4').forEach(el => el.classList.add('active'))

If you need legacy browser support, use a regular function or transpile and include this polyfill:

if (window.NodeList && !NodeList.prototype.forEach) {
    NodeList.prototype.forEach = function (callback, thisArg) {
        thisArg = thisArg || window
        for (let i = 0; i < this.length; i++) {
            callback.call(thisArg, this[i], i, this)
        }
    }
}

If you use querySelectorAll a lot, you can bind it to a variable:

const $$ = document.querySelectorAll.bind(document)

$$('.class1, .class2, .class3, .class4').forEach(el => el.classList.add('active'))