16. js 判斷變量類型，包括ES6 新類型Symbol

相信大家在開發中遇到需要判斷變量類型的問題，js變量按存儲類型可分為值類型和引用類型，值類型包括Undefined、String、Number、Boolean，引用類型包括object、Array、Function，

直接上辨別類型的封裝函數

function varType(n) {
    var typeStr = Object.prototype.toString.call(n);
    //var typeOfName = (typeof n);
    var typeName = '';
    switch (typeStr){
        case '[object String]':
            typeName = 'string';
            break;
       case '[object Number]':
           typeName = 'number';
           break;
       case '[object Boolean]':
           typeName = 'boolean';
           break;
       case '[object Undefined]':
           typeName = 'undefined';
           break;
       case '[object Object]':
           typeName = 'object';
           break;
       case '[object Array]':
           typeName = 'array';
           break;
       case '[object Null]':
           typeName = 'null';
           break;
       case '[object RegExp]':
           typeName = 'RegExp';
           break;
      case '[object Symbol]':
           typeName = 'symbol';
           break;
      case '[object JSON]':
           typeName = 'json';
           break;
      case '[object Math]':
           typeName = 'math';
           break;
      default:
           typeName = 'object';
     }
     return typeName;
};
console.log(varType("1"));
console.log(varType(1));
console.log(varType({}));
console.log(varType([]));
console.log(varType(function () {}));
console.log(varType(null));
console.log(varType(undefined));
console.log(varType(true));
console.log(varType(NaN));
console.log(varType(Symbol()));
console.log(varType(JSON));
console.log(varType(Date));
console.log(varType(Math));
console.log(varType(RegExp()));