// вспомогательная функция для создания ноды
function createNode(name, klasses) {
    var n = document.createElement(name);
    n.className = klasses;
    return n;
}
 
function l(x) {
    console.dir(x);
}
 
function hasClass(node, cls) {
    var pattern = "\\b" + cls + "\\b";
    var regEx   = new RegExp(pattern, "gi");
    return regEx.test(node.className);
}
 
function addClass(node, cls) {
    if (hasClass(node, cls)) {
        return null;
    }
    node.className += " " + cls;
    return node;
}
 
function removeClass(node, cls) {
    if (!hasClass(node, cls)) {
        return null;
    }
    var pattern = "\\b" + cls + "\\b";
    var regEx   = new RegExp(pattern, "gi");
    var temp = node.className.replace(regEx, "");
    temp = temp.replace(/\s{2,}/, " ").trim();
    node.className = temp;
    return node;
}
 
l(hasClass(createNode('div', 'test'), 'test')); // true
l(hasClass(createNode('div', 'test'), 'tes')); // false
 
l(hasClass(createNode('div', 'test1 test2'), 'tes')); // false
l(hasClass(createNode('div', 'test1 test2'), 'test1')); // true
 
l(addClass(createNode('div', 'test1'), 'test2'));
l(addClass(createNode('div', 'test1'), 'test1'));
 
l(removeClass(createNode('div', 'test1 test2 test3'), 'test1'));
l(removeClass(createNode('div', 'test1 test2 test3'), 'test2'));
l(removeClass(createNode('div', 'test1'), 'test2'));
l(removeClass(createNode('div', 'test1'), 'test1'));

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