怎么判断一个数据的类型

• 使用 typeof 关键字 [ 适用于基本数据类型]
• Object.prototype.toString.call() [适用于对象类型]

01 使用 typeof 关键字 [ 适用于基本数据类型]

    var str = "我是字符串";
    var num = 10;
    var bool = true;
    var func = function(){};

    console.log(typeof str);   //string
    console.log(typeof num);   //number
    console.log(typeof bool);  //boolean
    console.log(typeof func);  //function

02 当使用判断typeof对象类型的时候，呵呵了

    var myArr = [1, 2, 3];
    var myDate = new Date();
    var obj = {};
    
    console.log(typeof myArr);  //object
    console.log(typeof myDate); //object
    console.log(typeof obj);    //object

03 Object.prototype.toString.call() [适用于对象类型]

    var myArr = [1, 2, 3];
    var myDate = new Date();
    var obj = {};

    console.log(typeof myArr); //object
    console.log(typeof myDate);//object
    console.log(typeof obj); //object

    console.log(Object.prototype.toString.call(myArr));  //[object Array]
    console.log(Object.prototype.toString.call(myDate)); //[object Date]
    console.log(Object.prototype.toString.call(obj));    //[object Object]

04 判断数组：Array.isArray() -> 注意兼容问题

    var myArr = [1, 2, 3];
    var obj = {};

    console.log(Array.isArray(myArr)); //true
    console.log(Array.isArray(obj));   //false