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Element.prototype.hasClass = function (className) {
    return new RegExp(' ' + className + ' ').test(' ' + this.className + ' ');
};


Element.prototype.addClass = function (className) {
    if (!this.hasClass(className)) {
        this.className += ' ' + className;
    }
};



Element.prototype.removeClass = function (className) {
    var newClass = ' ' + this.className.replace(/[\t\r\n]/g, ' ') + ' '
    if (this.hasClass(className)) {
        while (newClass.indexOf( ' ' + className + ' ') >= 0) {
            newClass = newClass.replace(' ' + className + ' ', ' ');
        }
        this.className = newClass.replace(/^\s+|\s+$/g, ' ');
    }
};



Element.prototype.toggleClass = function (className) {
    var newClass = ' ' + this.className.replace(/[\t\r\n]/g, " ") + ' ';
    if (this.hasClass(className)) {
        while (newClass.indexOf(" " + className + " ") >= 0) {
            newClass = newClass.replace(" " + className + " ", " ");
        }
        this.className = newClass.replace(/^\s+|\s+$/g, ' ');
    } else {
        this.className += ' ' + className;
    }
};


var elem = document.getElementById('foo');
elem.addClass('bar');
alert(elem.hasClass('bar'));
elem.removeClass('bar');
alert(elem.hasClass('bar'));
elem.toggleClass('bar');
alert(elem.hasClass('bar'));