1. Array
2. Object
js null and array types which are considered object typeof
3. Check the type (typeof)
You may return: number, string, boolean, object, underfined, function
console.log(typeof(xiaopei)) object
console.log(typeof(xiaopei.name)) string
Undefined variable was not only placed typeof error, returns the string underfined
4. Type Conversion
Explicit type conversion
Implicit type conversion
isNaN (data) will be transformed with the first data Number methods to digital, and then determines
+ / - / + (plus or minus) method will be called number before the conversion operation
+ Sides around a string will be called string, the string is converted to both sides
- * / before the operation, the left and right sides call number
&& || !
> / </> = / <= / == /! = Call number method, Boolean () method
