Element.matches ()

元素匹配(selectorString)。

根据MDN Web Docs:

如果元素将被指定的选择器字符串选中，则element .matches()方法返回true;否则，返回false。

因此，您可以使用element .matches()来确定元素是否包含类。

const element = document.querySelector('#example'); console.log (element.matches (' . foo '));/ /正确的 <div id="example" class="foo bar"></div>

查看浏览器兼容性

这里有一个小片段，如果你试图检查元素是否包含一个类，而不使用jQuery。

function hasClass(element, className) {
    return element.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(element.className);
}

这说明元素可能包含多个用空格分隔的类名。

OR

您还可以将此函数分配给元素原型。

Element.prototype.hasClass = function(className) {
    return this.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(this.className);
};

并像这样触发它(非常类似于jQuery的.hasClass()函数):

document.getElementById('MyDiv').hasClass('active');

一个简化的联机程序:1

function hasClassName(classname,id) {
 return  String ( ( document.getElementById(id)||{} ) .className )
         .split(/\s/)
         .indexOf(classname) >= 0;
}

IE当然不支持数组的1 indexOf。网上有很多猴子补丁。

className只是一个字符串，所以您可以使用常规的indexOf函数来查看类列表是否包含另一个字符串。

Felix's trick of adding spaces to flank the className and the string you're searching for is the right approach to determining whether the elements has the class or not. To have different behaviour according to the class, you may use function references, or functions, within a map: function fn1(element){ /* code for element with class1 */ } function fn2(element){ /* code for element with class2 */ } function fn2(element){ /* code for element with class3 */ } var fns={'class1': fn1, 'class2': fn2, 'class3': fn3}; for(var i in fns) { if(hasClass(test, i)) { fns[i](test); } } for(var i in fns) iterates through the keys within the fns map. Having no break after fnsi allows the code to be executed whenever there is a match - so that if the element has, f.i., class1 and class2, both fn1 and fn2 will be executed. The advantage of this approach is that the code to execute for each class is arbitrary, like the one in the switch statement; in your example all the cases performed a similar operation, but tomorrow you may need to do different things for each. You may simulate the default case by having a status variable telling whether a match was found in the loop or not.

下面是一个不区分大小写的简单解决方案:

function hasClass(element, classNameToTestFor) {
    var classNames = element.className.split(' ');
    for (var i = 0; i < classNames.length; i++) {
        if (classNames[i].toLowerCase() == classNameToTestFor.toLowerCase()) {
            return true;
        }
    }
    return false;
}