javascript 类型检测

var str = ‘123‘;
var num = 2;
var boo = true;
var def = defined;
var nu = null;

typeof str 
typeof num 
typeof boo 
typeof def 

function getType(obj){
     return (obj === null) ? null : typeof(obj);
}

function isFunction(it){
    return Object.prototype.toString.call(it) === ‘[object Function]‘;
}
function isArray(it){
    return Object.prototype.toString.call(it) === ‘[object Array]‘;
}