Simple utility for manipulating attribute values like you would with classes.

attr.js

/**
 * Allows manipulation of attribute values in the same way that is commonly done with classes.
 * Written as a helper for http://amcss.github.io/
 * Use setPrefix() if you want to prefix all your attributes with "am-" or "data-am-", etc.
 * @see https://github.com/yui/yui3/blob/master/src/dom/js/dom-class.js
 * @exports attr
 * @example
 * attr.setPrefix(node, 'css-');
 * attr.toggle(node, 'badge');
 * attr.toggle(node, 'badge', 'large');
 */
(function() {
    var prefix = '';
    
    var attr = {
        has: function(node, attribute, value) {
            attribute = prefix + attribute;
            var nodeAttr = node.getAttribute(attribute);
            
            if (nodeAttr === null) {
                return false;
            } else if (value === undefined) {
                return true;
            } else {
                var re = new RegExp('(?:^|\\s+)' + value + '(?:\\s+|$)');
                return re.test(nodeAttr);
            }
        },

        add: function(node, attribute, value) {
            if (!this.has(node, attribute, value)) {
                attribute = prefix + attribute;
                node.setAttribute(attribute, [node.getAttribute(attribute), value].join(' ').trim());
            }
        },

        remove: function(node, attribute, value) {
            var prefixedAttr = prefix + attribute;
            
            if (value === undefined) {
                node.removeAttribute(prefixedAttr);
            } else if (this.has(node, attribute, value)) {
                node.setAttribute(prefixedAttr, node.getAttribute(prefixedAttr).replace(new RegExp('(?:^|\\s+)' + value + '(?:\\s+|$)'), ' ').trim());

                if (this.has(node, attribute, value) ) { // in case of multiple adjacent
                    this.remove(node, prefixedAttr, value);
                }
            }
        },

        toggle: function(node, attribute, value) {
            var has = !(this.has(node, attribute, value));
            
            var func = (has) ? this.add : this.remove;
            func.apply(this, arguments);
        },
        
        setPrefix: function(newPrefix) {
            prefix = newPrefix;
        }
    };
    
    // AMD
    if (typeof define === 'function' && define.amd) {
        define(function() {
            return attr;
        });
    } else {
        this.attr = attr;
    }
})();

attr.min.js

/* https://gist.github.com/chrisbateman/c3cf0bc3744817c9f98f/ */
(function(){var d="",f={has:function(a,b,c){b=d+b;a=a.getAttribute(b);return null===a?!1:void 0===c?!0:(new RegExp("(?:^|\\s+)"+c+"(?:\\s+|$)")).test(a)},add:function(a,b,c){this.has(a,b,c)||(b=d+b,a.setAttribute(b,[a.getAttribute(b),c].join(" ").trim()))},remove:function(a,b,c){var e=d+b;void 0===c?a.removeAttribute(e):this.has(a,b,c)&&(a.setAttribute(e,a.getAttribute(e).replace(new RegExp("(?:^|\\s+)"+c+"(?:\\s+|$)")," ").trim()),this.has(a,b,c)&&this.remove(a,e,c))},toggle:function(a,b,c){(this.has(a,
b,c)?this.remove:this.add).apply(this,arguments)},setPrefix:function(a){d=a}};"function"===typeof define&&define.amd?define(function(){return f}):this.attr=f})();