Native JavaScript hasClass()

Ciprian on Thursday, August 22, 2019 in JavaScript DOM

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These JavaScript snippets implement a native hasClass() function (inspired by jQuery and dubbed elementHasClass()), which checks if an element has a certain class.

// Method #1: Use JavaScript element.className
function elementHasClass(element, className) {
    return (element.className === className);
}

// Method #2: Use JavaScript element attribute getter
function elementHasClass(element, className) {
    return (indexOf(element.getAttribute(className)));
}

// Method #3: Use JavaScript element.className (RegEx)
function elementHasClass(element, className) {
    return element.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(element.className);
}

// Usage
if (elementHasClass(document.querySelector('.element'), 'active')) {
    // Do this or do that
}

A prototype approach to the above solution is:

// Method #4: Prototype
Element.prototype.elementHasClass = function(className) {
    return this.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(this.className);
};

// Usage
if (document.querySelector('.element').elementHasClass('active')) {
    // Do this or do that
}

Personally, I would steer away from the RegEx ones, namely methods 3 and 4.

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