数据类型

        console.log('typeof-int-number', typeof (1));
        console.log('typeof-object-object', typeof ({}));
        console.log('typeof-array-object', typeof ([]));
        console.log('typeof-null-object', typeof (null));
        console.log('typeof-empty-string', typeof (''));
        console.log('typeof-undefined-undefined', typeof (undefined));