js 检测变量类型

let type = function(t) {
  var p = ({}).toString.call(t);
  var typeObj = {
    "[object Object]": "Object",
    "[object Array]": "Array",
    "[object Number]": "Number",
    "[object String]": "String",
    "[object Function]": "Function",
    "[object Boolean]": "Boolean",
    "[object Null]": ‘Null‘,
    "[object Undefined]": "Undefined"
  }
  return typeObj[p] ? typeObj[p] : false;
};