validateOptions.js

// For supplying defaultOptions and providing optional validation
var validateOptions = function(options, defaultOptions, validOptions)
{
    if (options === undefined)
        return defaultOptions;
    
    var validatedOptions = defaultOptions;
    
    for (var k in options)
    {
        if (validOptions === undefined)
        {
            validatedOptions = options[k];
            continue;
        }
        
        if (k in validOptions)
        {
            validatedOptions = options[k];
            
            // Handle validOptions list
            if (Array.isArray(validOptions[k]))
            {
                if (validOptions[k].indexOf(options[k]) == -1)
                {
                    delete validatedOptions[k];
                }
            }
        }
    }
    
    return validatedOptions;
}

// createAlert Example (http://getbootstrap.com/components/#alerts-dismissible):
var createAlert = function(message, options)
{
    var defaultOptions = {
        alertClass: 'info',
        dismissable: true,
    };
    
    options = validateOptions(options, defaultOptions, {
        alertClass: ['success', 'info', 'warning', 'danger'],
        dismissable: [true, false],
        message: null
    });
    
    var alertDiv = $('<div />')
        .addClass('alert')
        .addClass('alert-' + options.alertClass)
        .attr('role', 'alert');
    
    if (options.dismissable)
    {
        var btn = $('<button />')
            .attr('type', 'button')
            .addClass('close')
            .attr('data-dismiss', 'alert')
            .attr('aria-label', 'Close')
            .appendTo(alertDiv)
        
        $('<span />')
            .attr('aria-hidden', 'true')
            .html('&times;')
            .appendTo(btn);
        
        alertDiv.addClass('alert-dismissible');
    }
    
    alertDiv.append(message);
    
    return alertDiv;
}

// Invoke
var defaultOptions = {
    alertClass: 'info',
    dismissable: true,
};

options = validateOptions(options, defaultOptions, {
    alertClass: ['success', 'info', 'warning', 'danger'],
    dismissable: [true, false],
    message: null
});

var newAlert = createAlert('Info alert message');