context.js

/**
 * Returns a function that uses it's first argument as the context
 * for a callback
 * @param  {Function} callback The callback to call
 * @return {Function}
 */
function context(callback) {
    return function() {
        var args = Array.prototype.slice.call(arguments);
        var context = args.shift() || this;

        return callback.apply(context, args);
    };
}