判断数据类型的方法

  var red = "shark";
  var orange = 123456;
  var yellow = true;
  var green = undefined;
  var cyan = null;
  var blue = ['a','s','d'];
  var magenta = {};
  var purple = function(){};
  var black = [red,orange,yellow,green,cyan,blue,magenta,purple];

• Array.isArray()：只能判别Array数据类型

  console.log(Array.isArray(blue));

• instanceof：只能判别Function、Object、Array

  console.log(purple instanceof Function);
  console.log(magenta instanceof Object);
  console.log(blue instanceof Array);

• typeof：不能判别null，Array，Object数据类型，返回值都是Object

  for(var i=0;i<black.length;i++){
      console.log(typeof black[i]);
  }

• Object.prototype.toString.call()：数据类型判别最佳方案

  for(var i=0;i<black.length;i++){
      console.log(Object.prototype.toString.call(black[i]));
  }