var myName = "Shelley"; String base type
alert (myname.length); Implicitly creates a string object with the same value as myname and executes the length method
In the example above, just a string primitive type is created, not a string object. Yes, it's true that in code it's just a variable myname that creates a string primitive type. However, when a string-related method is called on the variable, even when all string properties are included (including the length and strike method), the variable is treated as a string object instance.
In summary, when an object method is called on a base data type, JavaScript creates an object instance of the base data type, executes the method call, and destroys the temporary object. The same principle applies to data types such as numbers and Booleans.
JavaScript basic properties access to object properties and methods