/**
 * isFunction
 *
 * @param  {Object}  obj
 * @return {Boolean}     Returns true if object is a Function.
 */
function isFunction(obj) {
    return typeof obj === "function";
}

/**
 * isFunction
 *
 * @param  {Object}  obj
 * @return {Boolean} Returns true if object is a Function.
 */
function isFunction(obj) {
    return typeof obj === 'function';
}

use single quotes, change indention