js 判断是否有class

// 获取元素
var element = document.querySelector('.my-element');

// 判断是否包含特定class
if (element.classList.contains('specific-class')) {
    console.log('Element has the class!');
} else {
    console.log('Element does not have the class.');
}

// 获取元素
var element = document.querySelector('.my-element');

// 判断是否包含特定class
if (element.className.indexOf('specific-class') !== -1) {
    console.log('Element has the class!');
} else {
    console.log('Element does not have the class.');
}

// 获取元素
var element = document.querySelector('.my-element');

// 判断是否包含特定class
var regex = new RegExp('(\\s|^)' + 'specific-class' + '(\\s|$)');
if (regex.test(element.className)) {
    console.log('Element has the class!');
} else {
    console.log('Element does not have the class.');
}