document.getElementById("whatever").className += "classToKeep";

使用加号('+')附加类，而不是覆盖任何现有的类

div.classList.add("foo");
div.classList.remove("foo");

更多信息请访问https://developer.mozilla.org/en-US/docs/Web/API/element.classList

试试这个:

function hasClass(ele, cls) {
  return ele.className.match(new RegExp('(\\s|^)'+cls+'(\\s|$)'));
}
    
function removeClass(ele, cls) {
  if (hasClass(ele,cls)) {
    var reg = new RegExp('(\\s|^)'+cls+'(\\s|$)');
    ele.className=ele.className.replace(reg,' ');
  }
}

Edit

好的，完全重写。 已经有一段时间了，我学到了一些东西，评论也很有帮助。

Node.prototype.hasClass = function (className) {
    if (this.classList) {
        return this.classList.contains(className);
    } else {
        return (-1 < this.className.indexOf(className));
    }
};

Node.prototype.addClass = function (className) {
    if (this.classList) {
        this.classList.add(className);
    } else if (!this.hasClass(className)) {
        var classes = this.className.split(" ");
        classes.push(className);
        this.className = classes.join(" ");
    }
    return this;
};

Node.prototype.removeClass = function (className) {
    if (this.classList) {
        this.classList.remove(className);
    } else {
        var classes = this.className.split(" ");
        classes.splice(classes.indexOf(className), 1);
        this.className = classes.join(" ");
    }
    return this;
};

旧邮政 我刚在用这样的东西。这是我想到的一个解决办法…

// Some browsers don't have a native trim() function
if(!String.prototype.trim) {
    Object.defineProperty(String.prototype,'trim', {
        value: function() {
            return this.replace(/^\s+|\s+$/g,'');
        },
        writable:false,
        enumerable:false,
        configurable:false
    });
}
// addClass()
// first checks if the class name already exists, if not, it adds the class.
Object.defineProperty(Node.prototype,'addClass', {
    value: function(c) {
        if(this.className.indexOf(c)<0) {
            this.className=this.className+=' '+c;
        }
        return this;
    },
    writable:false,
    enumerable:false,
    configurable:false
});
// removeClass()
// removes the class and cleans up the className value by changing double 
// spacing to single spacing and trimming any leading or trailing spaces
Object.defineProperty(Node.prototype,'removeClass', {
    value: function(c) {
        this.className=this.className.replace(c,'').replace('  ',' ').trim();
        return this;
    },
    writable:false,
    enumerable:false,
    configurable:false
});

现在你可以调用myelement。removeclass ('myClass')

或者链它:myElement.removeClass("oldClass").addClass("newClass");

try:

function removeClassName(elem, name){
    var remClass = elem.className;
    var re = new RegExp('(^| )' + name + '( |$)');
    remClass = remClass.replace(re, '$1');
    remClass = remClass.replace(/ $/, '');
    elem.className = remClass;
}

我使用这个JS片段代码:

首先，我到达所有的类，然后根据我的目标类的索引，我设置className = ""。

Target = document.getElementsByClassName("yourClass")[1];
Target.className="";